Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.7566/JPSCP.38.011138

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.jmmm.2022.170000

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

In this study, the Sm2Fe17 powder was subjected to nitridation at 743 K under N2 pressures of 0.05 and 0.1 MPa to investigate the growth kinetics of Sm–Fe–N. Two-phase growth of the fully nitride (FN) Sm2Fe17N3 phase and the nitrogen-poor (NP) Sm2Fe17Nx phase (0 < x < 3; x denotes the nitrogen content) was observed using 57Fe Mössbauer spectroscopy. Although the x value was greater at 0.05 MPa than at 0.1 MPa in the early stage of nitridation, the opposite trend was observed in the later stage. At a nitrogenation time of 24 h, nitridation was nearly complete at 0.1 MPa, while x tended to saturate and did not reach 3 at 0.05 MPa. The nitridation process was discussed based on two simultaneous growth processes: (i) the diffusion of the nitrogen atom in the NP phase and (ii) the nucleation and growth of the FN phase. A process combining N2 pressure and nitrogenation, which facilitated nitrogenation under low N2 pressure and high N2 pressure at the beginning and end of the nitridation process, respectively, achieved faster nitridation than process with a single N2 pressure.

DOI： 10.1016/j.jmmm.2022.169295

Scopus

Language：English   Publisher：Journal of the Physical Society of Japan  

First-principles calculations show that the atomic disorder between Al and Ge does not destroy the half-metallic character of CrAlGe, and that its unique character is, however, destroyed by the swap between Cr and Al (or Ge). Our analysis of the X-ray diffraction patterns of CrAlGe indicates the existence of this swap disorder.

DOI： 10.7566/JPSJ.91.064706

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

Ferromagnetic L21 phase of Ni2MnAl with high order degree is difficult to synthesize because of low L21/B2 order-disorder transformation temperature. It is found that magnetic field accelerated the transformation from the antiferromagnetic disordered B2 to ordered L21 phase. Magnetization increased by in-magnetic-field annealing at 673 K, which indicated the acceleration of the ordering to L21 phase. Magnetic field effects on the B2/L21 order-disorder transformation were discussed based on magnetic-field-induced change of transformation temperature, enhancement of degree of order at annealing temperature, and reduction of critical radius of L21 nuclei. Growth kinetics of L21 phase were evaluated by Johnson-Mehl-Avrami equation, which indicated that 15-T annealing accelerated the growth of L21 phase 5.7 times faster than zero-field annealing. Our results showed that magnetic field can contribute to shortening the annealing time for synthesis of ferromagnetic L21-Ni2MnAl alloy.

DOI： 10.1016/j.jmmm.2021.168908

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Iron and Steel Institute of Japan  

<p>Tramp elements in steel, such as Cu and Sn, cannot be removed by acid treatment. Since these elements condense by repeating recycling process, leading to deterioration of strength. Therefore, the methods for avoiding condensation or removing tramp elements are required. In this study, in-magnetic-field annealing process was focused on because magnetic field is effective for diffusion, phase transformation, phase diagram and precipitation. In-magnetic-field annealing of Fe-1mass%Cu at 773 K was performed in 5 and 10 T for investigating precipitation behavior of supersaturated Cu. From microstructural observation, precipitation of Cu-rich phase in Fe-matrix, and magnetic field effect on itself were not observed clearly. Increase of the hyperfine field was detected for the samples annealed at 5 T by Mössbauer spectroscopy, indicating the enhancement of the Cu-precipitation. On the contrary, hyperfine field for 10T-annealed sample was slightly smaller than that for 0 T. Therefore, in-field annealing effect on Cu-precipitation became unclear at 10 T. These magnetic field effects were discussed in the viewpoints of the change of Cu–Fe phase diagram and the atomic diffusion under magnetic field. Difference of the magnetic field effects on precipitation between 5 T and 10 T is explained by the competition between the enhancement of the driving force of the precipitation and suppression of the atomic diffusion. The obtained results indicated that there is optimized magnetic field intensity for controlling Cu-precipitation.</p>

DOI： 10.2355/isijinternational.isijint-2021-404

Scopus

Language：English   Publisher：Physical Review B  

DOI： 10.1103/PhysRevB.103.094428

Scopus

Language：English   Publisher：公益社団法人 日本金属学会  

<p>Ferromagnetic Mn–Al–C (τ-phase) can be synthesized by a single-route conventional reactive sintering method. The maximum magnetization and coercivity were 75.8 Am²/kg and 57 mT, respectively. The τ-phase fraction was evaluated to be 81 mass% for Mn₅₅Al₄₅C₂ annealed at 1273 K. The τ-phase of Mn₅₅Al₄₅C₂ can be synthesized at an annealing temperature from 873 to 1273 K, whereas that of Mn₅₅Al₄₅ cannot be synthesized. It was indicated that the phase stability of the hcp-phase (ε-phase) was improved by adding carbon, resulting in an ε–τ transformation.</p>

DOI： 10.2320/matertrans.MT-M2020166

Scopus

Language：English   Publisher：公益社団法人 日本金属学会  

<p>Combined accelerating effects of ε–τ phase transformation by in-magnetic-field annealing and Zn-addition were investigated for Mn₅₃Zn₂Al₄₅ in magnetic fields up to 15 T. The in-field annealing for Zn-added sample accelerated the ε–τ transformation 16 times faster than Mn₅₅Al₄₅ at annealing temperature of 623 K. The reduction of magnetization after finishing ε–τ transformation was also more rapid than that of Mn₅₅Al₄₅. However, magnetic-field-induced acceleration of ε–τ phase transformation and suppression of precipitation of β-phase were observed for Zn-added alloy Mn₅₃Zn₂Al₄₅ annealed at 573 K. The obtained results suggested that the β-phase stabilized against both τ- and ε-phases by Zn-addition. Therefore, although the ε–τ transformation was efficiently accelerated by in-field annealing of Mn₅₃Zn₂Al₄₅, more precisely control of annealing time is required for obtaining high fraction of ferromagnetic τ-phase.</p>

DOI： 10.2320/matertrans.MT-M2020235

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.jallcom.2021.161310

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.jmmm.2021.168411

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1016/j.physb.2020.412379

Other Link： https://www.sciencedirect.com/science/article/pii/S0921452620303884

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1016/j.jallcom.2020.155193

Other Link： https://www.sciencedirect.com/science/article/pii/S0925838820315565?via%3Dihub

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

<p>The spin reorientation and Curie temperature of Mn₂₋<i>_x</i>Fe<i>_x</i>Sb₁₋<i>_y</i>Sn<i>_y</i> (0 ≤ <i>x</i>, <i>y</i> ≤ 0.15) compound were investigated by magnetization measurements. Spin reorientation temperature increased from 255 K at <i>x</i> = 0 to 383 K at <i>x</i> = 0.15, whereas it almost unchanged by Sn substitution. Curie temperature decreased down to 518 K with both Fe and Sn substitution. Substitution of Fe stabilized the ferrimagnetic state with magnetic moment lying in <i>c</i>-plane. Substitution of Sn induced the antiferromagnetic phase at low temperature. It was found that the magnetic hysteresis derived from quasi first-order magnetic phase transition exhibited at <i>x</i> ≥ 0.10 or <i>T</i> ≥ 300 K.</p>

DOI： 10.2320/matertrans.mt-mn2019016

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

<p>Nitrogenation of Sm₂Fe₁₇ powder was performed under a zero field and a magnetic field of 5 T at 623, 673 and 743 K to clarify the magnetic field effect on nitrogenation. Applying a magnetic field of 5 T induced nitrogenation compared with zero-field nitrogenation, and almost fully nitride Sm₂Fe₁₇N_2.9 was obtained at 743 K. Mössbauer spectroscopy results suggested that a 5-T magnetic field promoted the phase transformation to the fully-nitride Sm₂Fe₁₇N₃ phase. The magnetic field effect was discussed based on the magnetic energy gain and magnetic properties of host Sm₂Fe₁₇ and fully nitride Sm₂Fe₁₇N₃.</p>

DOI： 10.2320/matertrans.mt-mn2019012

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi:10.2320/matertrans.MT-MN2019013

Other Link： https://www.jstage.jst.go.jp/article/matertrans/61/8/61_MT-MN2019013/_article

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：日本金属学会  

DOI： https://doi.org/10.2320/materia.59.422

Other Link： https://www.jstage.jst.go.jp/article/materia/59/8/59_422/_article/-char/ja/

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.2320/matertrans.MT-MN2019016

Other Link： https://www.jstage.jst.go.jp/article/matertrans/61/8/61_MT-MN2019016/_article

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

<p>Pressure effects on magnetic susceptibility χ and energy gap <i>E</i>_g⁰ of narrow-gap semiconductor FeSb₂ were investigated for the temperature range of 50–300 K and pressures up to 13 kbar. The estimated <i>E</i>_g⁰ for ambient pressure, <i>E</i>_g0(0), was 29 meV. By application of pressure, χ was suppressed, and <i>E</i>_g0(<i>P</i>) was estimated to be 52 meV for 13 kbar. The fourth-order expansion coefficient γ of the free energy in magnetization was positive and enhanced by applying pressures.</p>

DOI： 10.2320/matertrans.mt-mn2019015

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

<p>The magnetization measurements were carried out for polycrystalline Au₄V in magnetic fields up to 130 kOe. The spontaneous magnetic moment <i>p</i>_s was determined to be 0.255 μ_B/V at 4 K by high field magnetization. The magnetization process was analyzed on the basis of Takahashi’s spin fluctuation theory for weak itinerant electron ferromagnets. The characteristic parameters of the spin fluctuation were estimated to be <i>T</i>_A = 1.3 × 10³ K and <i>T</i>₀ = 2.3 × 10³ K using the data for 110–130 kOe.</p>

DOI： 10.2320/matertrans.mt-mn2019011

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.2355/isijinternational.ISIJINT-2019-470

Other Link： https://www.jstage.jst.go.jp/article/isijinternational/60/4/60_ISIJINT-2019-470/_article

Language：Japanese   Publishing type：Research paper (scientific journal)  

© 2019 Elsevier B.V. X-ray powder diffraction, differential scanning calorimetry, and magnetization measurements were performed to investigate the effects of heat treatment on the magnetic and structural properties of as-cast and aging treated MnCoGe. The martensitic transformation temperature of the as-cast sample was 526 K for its first heating cycle, which decreased with repeating thermal cycles of 300–1273 K. MnCoGe prepared by aging treatment of 873 K for 7 days showed a first-order magnetic transition, which was accompanied by a martensitic transformation at 307 K. However, the transformation was not detected when the aging temperature was increased up to 973 K. The martensitic transformation temperature and volume of the parent phase was found to have a positive correlation.

DOI： 10.1016/j.jmmm.2019.166199

Scopus

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

DOI： http://hdl.handle.net/10232/00030849

Other Link： http://hdl.handle.net/10232/00030849

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

<p>In-field heat treatments of an Mn–Ga diffusion couple were performed at 773 K for 12, 24 and 48 h to investigate the phase formation under magnetic fields. Formation of the MnGa₃, Mn₂Ga₅, MnGa, Mn₃Ga₂ and β-Mn phases was confirmed for magnetic fields of 0 T and 5 T. For a diffusion-controlled process, there is a parabolic relationship between the thickness of the phase layers and annealing time for the MnGa and Mn₂Ga₅ phases. The parabolic coefficients of MnGa and Mn₂Ga₅ for a zero magnetic field were determined as 8.7 × 10⁻³ µm²s⁻¹ and 4.6 × 10⁻¹ µm²s⁻¹ respectively. For a magnetic field of 5 T, the parabolic coefficients were evaluated as 11 × 10⁻³ µm²s⁻¹ for the MnGa phase and 4.5 × 10⁻¹ µm²s⁻¹ for the Mn₂Ga₅ phase.</p>

DOI： 10.2320/matertrans.mt-maw2019013

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

<p>An in-field heat treatment furnace utilized for a magnet with a 50 mm room-temperature bore was made to study magnetic field effect on gas-solid reaction. Using this furnace, nitridation of Sm₂Fe₁₇ powder was performed under a 5-T magnetic field and a 0.1-MPa nitrogen gas pressure for the temperature range 623 to 743 K. Applying a magnetic field of 5 T promoted nitridation by approximately 0.6 nitrogen atoms per formula unit compared with zero-field nitridation, and almost fully nitride Sm₂Fe₁₇N_2.9 was obtained at 743 K.</p>

DOI： 10.2320/matertrans.mt-maw2019009

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Language：English   Publishing type：Research paper (scientific journal)  

© 2018 Author(s). The magnetic properties of Mn1-xTMxAlGe (TM = V, Fe and Cu) were investigated for x ≤ 0.2. The spontaneous magnetization decreased with increasing x. A remarkable decrease in the Curie temperature TC was observed for TM = Fe. For ferromagnetic MnAlGe (x = 0) and TM = nonmagnetic Cu (x = 0.2), Curie-Weiss law was confirmed. The compounds with TM = V and Fe (x = 0.2) did not show Curie-Weiss law, and the data of reciprocal susceptibility vs. temperature bent, indicating change of the magnetism from ferromagnetism. Obtained results suggested that the magnetic moments of V and Fe were aligned antiparallel to those of Mn, resulting in the ferrimagnetism-like behavior.

DOI： 10.1063/1.5043069

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1063/1.5043069

Other Link： https://aip.scitation.org/doi/full/10.1063/1.5043069

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1063/1.5043105

Other Link： https://aip.scitation.org/doi/full/10.1063/1.5043105

Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.1063/1.5042834

Other Link： https://aip.scitation.org/doi/full/10.1063/1.5042834

Language：Japanese   Publishing type：Research paper (scientific journal)  

© 2018 Elsevier B.V. The magnetic and structural properties of Mn1−xCrxAlGe (0 ≤ x ≤ 1.0) compounds were investigated. The spontaneous magnetization Ms and Curie temperature TC of Mn1−xCrxAlGe has a cusp at x = 0.2. The maximum values of Ms and TC are 1.74 μB/f.u. and 601 K, respectively. It was found that the tetragonal Cu2Sb-type structure was stable for 0 ≤ x ≤ 0.75, whereas orthorhombic TiSi2-type structure was observed for x ≥ 0.8. The reciprocal susceptibility as a function of temperature suggested that the magnetic moment of Cr is antiferromagnetically coupled with that of Mn in Cu2Sb-type structure.

DOI： 10.1016/j.jmmm.2018.02.022

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Scopus

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Physics Publishing  

Fe2MnSi exhibits a ferromagnetic transition at TC and another transition to a phase with antiferromagnetic components at a low temperature of TA . By substituting V for Mn, so as to obtain Fe2Mn1-xV x Si, TA decreases with x and then vanishes around x ∼ 0.2. In this study, the magnetic transitions are investigated by magnetization measurements for Fe2Mn1-xV x Si (y = 1, 0 ≤ x ≤ 0.2) in high magnetic fields up to ∼70 T and for Fe1.5(Mn1-xV x )1.5Si (y = 1.5, 0 ≤ x ≤ 0.1) up to 5 T. For y = 1.5, with increasing x, TC increases and TA decreases as for y = 1, and the rate of the decrease in TA with x is slightly smaller than for y=1. In the low magnetic field region, TA for y = 1 does not significantly change due to the magnetic field but a distinct decrease is observed in high fields. The critical field at 0 K of this transition in Fe2MnSi is found to be larger than 70 T, and with increasing x, the critical field decreases corresponding to the decrease of TA at zero field.

DOI： 10.1088/1742-6596/969/1/012099

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

The Pressure effect on the magnetic properties of the weak itinerant electron ferromagnet CrAlGe was investigated at pressures up to 1.0 GPa. The spontaneous magnetic moment p(s) and Curie temperature T-C decreased with increasing applied pressure P. The pressure derivatives of p(s) and T-C were dp(s)/dP = -3.98 x 10(-5) mu(B)/MPa and dT(C)/dP = -6.58 x 10 K-3/MPa, respectively. These obtained results are discussed on the basis of Takahashi's spin fluctuation theory for weak itinerant electron ferromagnets. The characteristic parameters T-0 and T-A increased with pressure.

DOI： 10.7566/JPSJ.87.014701

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Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

<p>The magnetic and structural properties of ferrimagnetic (FRI) Mn_1.9Fe_0.1Sb_0.9Sn_0.1 with a Cu₂Sb-type tetragonal structure were studied by magnetization and high field X-ray diffraction (XRD) measurements in 10 ≤ <i>T</i> ≤ 773 K and in magnetic fields μ₀<i>H</i> up to 5 T. The lattice parameters <i>a</i> and <i>c</i> at 285 K were estimated to be 0.407 nm and 0.655 nm, respectively. The saturation magnetization at 10 K was determined to be 39.1 Am²/kg. It was observed that a first order magnetic transition (FOMT) with a thermal hysteresis occurred in the vicinity of 310 K under low magnetic fields. This FOMT disappeared easily by applying magnetic fields over 0.4 T.</p>

DOI： 10.2320/matertrans.m2017291

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Scopus

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Publisher：Metals  

DOI： 10.3390/met7090364

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/LMAG.2016.2616843

Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publisher：IEEE Magnetics Letters  

DOI： 10.1109/LMAG.2017.2687878

Scopus

Language：English   Publisher：IEEE Magnetics Letters  

DOI： 10.1109/LMAG.2016.2617859

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

DOI： 10.1109/LMAG.2016.2621733

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Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1063/1.4961338

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.2320/matertrans.M2015382

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.2320/jinstmet.J2015055

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.jmmm.2015.07.114

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

Structural, magnetic and thermal properties of ferromagnetic MnCo1-xFexGe (0 &lt;= x &lt;= 0.12) compounds were investigated. The Curie temperature T-C and the martensitic transformation temperature T-M of MnCoGe (x = 0) were determined to be 340 K and 510 K, respectively. With increasing x from 0 to 0.08, T-M decreased and reached room temperature (290 K) for x similar to 0.08. For x &gt; 0.09, MnCo1-xFexGe did not exhibit the martensitic transformation. The compound for x similar to 0.08 showed a first-order magnetic transition with a thermal hysteresis of 20 K and was accompanied by the martensitic transformation in the vicinity of room temperature. The phase diagram of MnCo1-xFex Ge (0 &lt;= x &lt;= 0.12) is presented.

DOI： 10.1063/1.4961336

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Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1016/j.phpro.2015.12.126

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Other Link： http://hdl.handle.net/10232/26366

Authorship：Lead author   Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Other Link： http://hdl.handle.net/10232/26364

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1016/j.phpro.2015.12.148

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

We applied first-principles total-energy calculations to several compounds Mn₂₋<i>_x</i>M<i>_x</i>Sb (M = Ti, Cr, Co, or Cu) to calculate the total energy. The results indicate that the Ti and Cu (Cr and Co) atoms prefer the Mn(II) site to the Mn(I) site [Mn(I) to Mn(II)]. These results are consistent with experimental observations. The antiferromagnetism (AF) [ferrimagnetism (FR)] is more stable than FR (AF) upon decreasing (increasing) the distance between the Mn(II) and Sb atoms in the <i>z</i> direction in all Mn₂₋<i>_x</i>M<i>_x</i>Sb systems. This result indicates that the environment around the Mn atom plays a very important role in the stabilization of the AF state, as is the case with Mn₂Sb₁₋<i>_x</i>As<i>_x</i> systems. For Mn₂₋<i>_x</i>Co<i>_x</i>Sb systems, the atomic disorder between the Mn and Co atoms is insensitive to the relative stability of two magnetic phases AF and FR.

DOI： 10.2320/matertrans.m2014417

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Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (other academic)  

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Language：English   Publishing type：Research paper (scientific journal)  

Language：English  

DOI： 10.7566/JPSCP.3.011003

Language：Japanese   Publisher：The Japan Society of Calorimetry and Thermal Analysis  

The magnetic field effect on the α–γ transformation of hypoeutectoid steels (Fe-0.1wt.%C, Fe-0.23wt.%C, and Fe-0.47wt.%C) were investigated by differential thermal analysis under high magnetic fields <i>B</i> up to 26 T. The magnetic field effects for the transformation temperatures A₁ (αFe + Fe₃C → α-Fe + γ-Fe) and A₃ (α-Fe + γ-Fe → γ-Fe) were different from each other. The increment of A₁ induced by the magnetic field was independent from the carbon concentration. A₁ increased linearly for the magnetic field for <i>B</i> < 10 T, whereas A₁ increased quadratically for <i>B</i> > 20 T. A₃ for Fe-0.23 wt.%C increased quadratically against <i>B</i>. When the magnetic field of 26 T was applied, A₁ and A₃ for Fe-0.47wt.%C increased 35 K and 53 K, respectively. The magnetic field effects for the A₁ and A₃ are discussed on the basis of the gain of Zeeman energy for α-Fe.

DOI： 10.11311/jscta.41.2_43

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

The electronic and magnetic properties of Mn₂Sb₁₋<i>_x</i>As<i>_x</i> (where <I>x</I> = 0,0.5,1) are investigated from first-principles total-energy calculations. The predicted magnetic ground states (ferrimagnetism for <i>x</i> = 0 and antiferromagnetism for <i>x</i> = 1) are in agreement with experimental observations; however, this is not the case for <i>x</i> = 0.5. Here, it is found that the artificial change of the surrounding atoms of Mn stabilizes the antiferromagnetism. A similar change stabilizes ferrimagnetism (antiferromagnetism) for <i>x</i> = 1 (<i>x</i> = 0). These results indicate that the environment around the Mn atoms plays a very important role in the stabilization of antiferromagnetism in the Mn₂Sb₁₋<i>_x</i>As<i>_x</i> system. In addition, an analysis of the sign of an effective exchange interaction as a function of the distance between the Mn atoms is performed.

DOI： 10.2320/matertrans.m2014251

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

The magnetic field effect (MFE) on liquidus boundary of Bi-Mn binary system was investigated by differential thermal analysis (DTA) and the computer coupling of phase diagram method (CALPHAD). The liquidus boundary for Bi-18at.% Mn and Bi-24at.%Mn rose clearly by the application of the magnetic fields. The MFE for liquidus boundary temperature T-liq changed from Delta T-liq proportional to B-2 to Delta T-liq proportional to B because of the large increase of the peritectic temperature from BiMn and BiMn1.08 by the application of magnetic field.

DOI： 10.1063/1.4897725

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

The structural and magnetic properties of Heusler alloy Ni₄₆Mn₄₁In₁₃ were studied by magnetization and X-ray powder diffraction measurements in the 4.5–350 K temperature range and in magnetic fields up to 5 T. The alloy undergoes martensitic transformation from a <i>L</i>2₁-type cubic structure with <i>a</i>_c = 0.600 nm at 293 K to a six-layered monoclinic (6<i>M</i>) structure in the transition temperature of 160–230 K. The lattice parameters for the 6<i>M</i> structure were estimated to be <i>a</i>_m = 0.441 nm, <i>b</i>_m = 0.557 nm, <i>c</i>_m = 1.30 nm, α_m = 90.0°, β_m = 94.0°, and γ_m = 90.0° at 75 K. In this transformation from the <i>L</i>2₁ to 6<i>M</i> structures, the cell volume contracts by 0.34% at 8 K. In addition, we observed the magnetic field-induced reverse transformation of this alloy.

DOI： 10.2320/matertrans.m2013372

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

We investigated the structural properties and electrical characteristics of GdTiO3 dielectrics for IGZO TFT devices. We used XRD, XPS, and AFM to examine the structural, compositional, and morphological features of the GdTiO3 film, respectively. The IGZO TFT featuring a GdTiO3 gate dielectric exhibited a large field-effect mobility of 32.3 cm(2) V-s, a small threshold voltage of 0.14 V, a high Ion/Ioff current ratio of 4.2 x 10(8), and a low subthreshold swing of 213 mV/decade.

DOI： 10.1109/IVESC.2014.6891962

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Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：KOREAN PHYSICAL SOC  

Magnetization and electrical resistivity measurements were carried out for polycrystalline Mn2Sb1-x Ge (x) (0.05 a parts per thousand currency sign x a parts per thousand currency sign 0.2) in magnetic fields up to 16 T in the 4.2 - 600 K temperature range in order to investigate the magnetic and the electrical properties under high magnetic fields. Mn2Sb0.92Ge0.08 showed a Curie temperature, T (C) , of 532 K and a first order magnetic transition from a ferrimagnetic (FRI) to an antiferromagnetic (AFM) phase at T (t) = 230 K with decreasing temperature in a zero magnetic field. With increasing x, T (C) decreased and T (t) increased. For Mn2Sb0.92Ge0.08, a matamagnetic transition from an AFM to a FRI phase was observed at 215 K. The magnetic phase diagram of Mn2Sb1-x Ge (x) is presented.

DOI： 10.3938/jkps.63.747

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Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publisher：Nutrition  

Objective: Anorexia nervosa (AN) continues to be a refractory disease because of its unknown pathogenesis. The role of adiponectin in AN has not been clarified. Moreover, few reports have described the relations between adiponectin isoforms and AN in the physical and psychological states. Therefore, we measured plasma adiponectin and its isoforms levels in patients with AN to examine their roles in AN. Methods: Eighteen women participated in this study: nine patients with AN and nine age-matched healthy controls. We examined plasma adiponectin and its isoforms levels in all subjects and administered three types of psychological test to patients with AN: the Eating Disorders Inventory-2, the Maudsley Obsessional-Compulsive Inventory, and the Beck Depression Inventory-2. Results: We found that the percentage of high-molecular-weight (HMW) to total adiponectin (%HMW) was significantly low and the percentage of low-molecular-weight (LMW) to total adiponectin (%LMW) was significantly high in the AN group compared with the control group. The %HMW positively and the %LMW negatively correlated with body mass index in the entire study population. The %HMW was also positively correlated with psychological symptoms such as social insecurity or cleaning evaluated with the Eating Disorders Inventory-2 or the Maudsley Obsessional-Compulsive Inventory. Conclusions: Our study indicates that all adiponectin isoforms should be evaluated in patients with AN in addition to total adiponectin. The decreased %HMW and the increased %LMW that were correlated with the body mass index and some components of psychopathology in our patients may indicate a complex role of adiponectin isoforms in maintaining energy homeostasis and emotion during extreme malnourishment. © 2013 Elsevier Inc.

DOI： 10.1016/j.nut.2012.07.011

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.68.2.3.0_399_4

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

First-principles total-energy calculations have been performed for the hypothetical case of <i>x</i> = 1 in Mn₂₋<i>_x</i>X<i>_x</i>Sb (X = Co and Cu) for several magnetic states, using the full-potential linearized augmented plane wave method based on the generalized gradient approximation. The calculated total energy indicates that the Co (Cu) atom prefers the site Mn(I) to the site Mn(II) (Mn(II) to Mn(I)). This result of Co is consistent with the available neutron diffraction experiment. For CoMnSb where Co occupies the site Mn(I), the change of lattice constants (<i>a</i> and <i>c</i>) and <i>c</i>/<i>a</i> from AF2 to F is in good agreement with experimental trends. Our results indicate that the optimization of the ratio <i>c</i>/<i>a</i> (lattice distortion) is crucial to determine the most stable magnetic state and that the optimization of the atomic positions of the sites Mn(II) and Sb is also crucial.

DOI： 10.2320/matertrans.m2013327

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

Magnetization, electrical resistivity and X-ray diffraction measurements were carried out for Mn_1.8Co_0.2Sb with a tetragonal structure in 4.2 ≤ <i>T</i> ≤ 280 K and in field <i>B</i> up to 16 T. For <i>B</i> = 0 T, anisotropic structural deformation occurred at <i>T</i>_t ∼ 140 K for zero-field cooling (ZFC), accompanied by a first-order magnetic transition from the ferrimagnetic (FRI) to antiferromagnetic (AFM) phases. In this deformation, the lattice parameters <i>a</i> and <i>c</i> changed by Δ<i>a</i>/<i>a</i> = +0.15% and by Δ<i>c</i>/<i>c</i> = −0.44%, respectively. By applying magnetic fields of 5 T, <i>T</i>_t decreased to 60 K with thermal hysteresis of 35 K. The two-phase coexistence of the AFM and residual FRI phases was observed even at 10 K for field cooling of 5 T, while a single phase of AFM was confirmed for ZFC. At <i>B</i> = 16 T, the transition did not occurs. In addition, a field-induced structural deformation was observed, accompanied by the metamagnetic transition just below <i>T</i>_t. The obtained results are discussed from a viewpoint on entropy change for the transition.

DOI： 10.2320/matertrans.m2012415

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Magnetics Society of Japan  

  Fully-epitaxial NbN/Co₂MnSi bilayer films were grown on MgO(001) single crystalline substrates by a sputter technique. Structural, electric transport and magnetic properties were investigated for the fabricated films. The resulting NbN/Co₂MnSi bilayer films show superconducting critical temperature <i>T</i>_c was of 16.0 K and the saturation magnetization <i>M</i>_s at room temperature was of 790 emu/cm³. The electric resistivity of the fabricated films was also measured under magnetic fields and the upper critical field <i>B</i>_c2 was estimated to be<i>B</i>_c2 > 30 T in the case of the applied magnetic field parallel to the MgO(001) single crystalline substrate. In addition, NbN/Co₂MnSi junctions were made by an electron-beam lithography technique. The enhancement of a zero-bias conductance peak (ZBCP) was observed in differential conductance in the NbN/Co₂MnSi junctions. The ZBCP disappeared above <i>T</i>_c = 16.0 K of superconducting NbN films.

DOI： 10.3379/msjmag.1305r007

Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.68.1.3.0_537_3

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

To examine magnetic field effects on the Bi–Mn equilibrium phase, a high-magnetic fields differential thermal analysis (HF-DTA) was performed for fields up to 18 T and temperatures ranging from 300 to 753 K. For zero field, the peritectic temperatures <i>T</i>_p1 (BiMn_1.08 + Bi-rich liquid → BiMn) and <i>T</i>_p2 (αMn + Bi-rich liquid → BiMn_1.08), and the eutectic temperature <i>T</i>_E (the Bi-rich liquid → Bi solid + BiMn) were determined to be 632, 721 and 538 K, respectively. The Bi–Mn phase diagram at 18 T was obtained, which showed that <i>T</i>_p1 increases with increasing magnetic fields at the rate of 2 K T⁻¹. Furthermore, the liquidus boundary temperature <i>T</i>_liq between BiMn_1.08 + liquid and Bi-rich liquid was found to increase nonlinearly with increasing magnetic field.

DOI： 10.2320/matertrans.m2012310

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Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We have demonstrated the effect of pressure on the steplike metamagnetic transition and its associated magnetostriction in (Eu1-xGdx)(0.6)Sr0.4MnO3 (x=0 and 0.1). The critical field initiating the field induced ferromagnetic transition in both samples is lowered by the applied pressure. The further application of external pressure up to 1.2 GPa on the x=0 parent sample causes a spontaneous ferromagnetic transition with a second-order like character, leading to collapses of the steplike transition and its concomitant lattice striction. These findings indicate a crucial role of the low-temperature phase separated state characterized by a suppressed magnetization upon decreasing temperature. (C) 2012 Elsevier BY. All rights reserved.

DOI： 10.1016/j.jmmm.2012.06.036

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Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOP PUBLISHING LTD  

alpha-Dy2S3 possesses orthorhombic crystal structure having two crystallograpically inequivalent Dy sites. Magnetization process of alpha-Dy2S3 single crystal after cooling in the high magnetic field of 18 T has been investigated. The magnetization under the field of 18 T along the a-axis on the cooling process from 150 K shows step-like rises at 70 and 40 K and reaches about 9 mu(B) per one Dy3+ at 1.5 K. This value, which corresponds to 90 % of full saturation moment of Dy3+, is much larger than 6 mu(B) obtained at the same conditions after cooling in no magnetic field (zero-field cooling; ZFC). After cooling to 1.5 K, the magnetization while decreasing field shows abrupt drops at 3.0 and 1.7 T, and then comes to 0 mu(B) at 0 T. Subsequently, while increasing field, the magnetization demonstrates a similar curve to that obtained after ZFC without step-like rise below 13.1 T. At mu H-0 = 13.1 T, the magnetization rises suddenly and agrees with the curve for the decreasing process. This irreversible magnetization process yields extremely broad hysteresis having width of mu(0)Delta H = 11.4 T. Broader hysteresis and narrower one are also observed at 4.2 and 10 K, respectively.

DOI： 10.1088/1742-6596/400/3/032010

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Metals and Materials  

  Measurements of magnetization, electrical resistivity and high field X-ray powder diffraction (XRD) were carried out for polycrystalline Mn_1.8Co_0.2Sb in magnetic fields up to 5 T in 4.2-300 K temperature range, in order to investigate the structural properties affected by magnetic fields. In a zero field, the compound shows the first-order magnetic transition from the ferrimagnetic (FRI) to antiferromagnetic (AFM) states at <i>T</i>_t=145 K with decreasing temperature. By applying magnetic fields of 5 T, <i>T</i>_t decreased to 60 K with thermal hysteresis of 35 K. From the XRD measurements, not only the AFM phase but also the residual FRI phase was confirmed even at 10 K in cooling process under 5 T. Results obtained indicate that the residual FRI phase is kinetically arrested.<br>

DOI： 10.2320/jinstmet.76.246

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Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (other academic)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We studied temperature and magnetic field dependence of magnetization, M(T) and M(B), on thiospinel FeCr2S4. We observed a step-like anomaly at T-00 similar to 9 K for M(T) attributed to an orbital order transition in magnetic field 0 &lt;B &lt;= 7 T. Furthermore, also for M(B), the step-like anomaly appears at B-c similar to 5.5 T below T-00. This suggests an existence of a magnetic phase boundary at B-c in T &lt; T-00. Because the anomaly at B-c of M(B) exists in the orbital ordered phase, the spin structure of FeCr2S4 in T &lt; T-00 is strongly coupled with the lattice of the system. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2011.07.041

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Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Martensitic transformation in a highly ordered Fe3Pt has been investigated by magnetization and X-ray diffraction measurements. We confirmed that a new type of face-centered tetragonal (FCT) martensite phase appears below 60 K in Fe3Pt with a degree of order S = 0.88. The tetragonality c/a gradually increases with decreasing temperature, and is approximately 1.005 at 10 K. This is in contrast to the tetragonality c/a &lt; 1 generally observed in the FCT martensite with a degree of order less than 0.8. The spontaneous magnetization increases in association with the transformation. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2011.06.035

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Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

Ferromagnetic shape memory effects of antiperovskite Mn3CuN are markedly altered by nitrogen deficiency. The martensitic transformation occurs at a lower temperature than ferromagnetic ordering for nitrogen-deficient Mn3CuN0.8, although they both occur simultaneously for stoichiometric Mn3CuN. In the martensitic phase, Mn3CuN0.8 contracts in a direction parallel to the magnetic field, in contrast to the expansion observed in Mn3CuN, implying that the easy axis is converted from the longer a axis in Mn3CuN to the shorter c axis in Mn3CuN0.8. The operating magnetic field for magnetostriction drastically decreases for Mn3CuN0.8, suggesting a possible supermagnetostriction around the critical compositional region for the easy-axis conversion.

DOI： 10.1143/JPSJ.79.073706

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Elsevier B.V.  

We have investigated martensitic transformation in a highly ordered Fe 3Pt by X-ray diffraction measurements. We found that a new type of FCT martensite phase appears in Fe3Pt with degree of order S = 0.88. In this martensite phase, the tetragonality c/a of the martensite is approximately 1.005 at 10 K, being different from that of so far known FCT martensite phase with c/a &lt
1.

DOI： 10.1016/j.phpro.2010.11.085

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Language：English   Publishing type：Research paper (scientific journal)  

The results of a comprehensive study of the structural, magnetic, and magnetotransport properties of the Heusler compounds Ru2-x Fex CrSi are presented. The Fe-rich compounds (x 1.5) exhibit a usual ferromagnetic transition. The Ru-rich compound (x=0.1) does not show ferromagnetism but exhibits a peak in magnetic susceptibility at TN =30K. Nevertheless, specific-heat measurements show that there is no antiferromagnetic transition at TN nor at any other temperatures. With further decreasing temperature strong irreversible behavior occurs below a temperature Tg. It is proposed that these results can be interpreted as successive spin-glass transitions at TN and Tg. The compounds with intermediate x (=0.3 and 0.5) are found to be ferromagnetic. Both the saturation magnetization and the Curie temperature TC increase with increasing x. However, being different from the Fe-rich compounds, hysteresis of the magnetization is observed and this suggests that the ferromagnetism has glassy character. In lower-temperature range fairly large negative magnetoresistance are observed. These results are suggestive of a magnetically inhomogeneous ferromagnetic state, that is, the formation of ferromagnetic clusters. © 2009 The American Physical Society.

DOI： 10.1103/PhysRevB.79.224423

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Study of magnetostriction of (Lu(0.8)Ce(0.2))(2)Fe(17) has been performed by two methods, bulk and microscopic: by the capacitor dilatometer on a single crystal grown by the Czochralski method and by the X-ray powder diffraction. The field-induced transition from the antiferromagnetic to the ferromagnetic state is accompanied by the lattice expansion both in the basal plane and along the c-axis of the hexagonal structure. In addition to the spontaneous linear magnetostriction lambda(s)(a) = 0.8 x 10(-3), lambda(s)(c) = 6.8 x 10(-3) along the a and c axes, respectively, and volume effect omega(s) = 8.4 x 10(-3), a comparable field-induced magnetostriction (lambda(a) = 1.3 x 10(-3), lambda(c) = 3.4 x 10(-3), omega = 6.0 x 10(-3)) is observed in a field of 5T applied along the a-axis. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2008.11.003

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

The ab-plane infrared and optical reflectance of single-crystal Bi2Sr2CoO6+delta (0.4 &lt;delta &lt; 0.5) have been measured over a wide frequency range (50-55000 cm(-1)) and at temperatures between 20 and 330 K. The room-temperature infrared spectrum displays an insulating characteristic. The optical gap determined from the infrared conductivity (similar to 0.53 eV) is consistent with thermal activation energy from dc transport measurements. Upon passing through the 265 K antiferromagnetic ordering transition, a softening of the phonon mode near 205 cm(-1) correlates well with the temperature-dependent normalized square of the sublattice magnetization. Furthermore, the magnetic-order-induced splitting of the phonon modes at about 238 and 376 cm(-1) is observed. Additionally, the phonon mode at about 588 cm(-1) exhibits a Fano-type line shape. Since no appreciable structural change was detected at low temperatures in x-ray diffraction studies, all of these observables suggest a complex nature of spin-phonon coupling in this material.

DOI： 10.1103/PhysRevB.79.155109

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

We report a significant decrease in the low-temperature resistance induced by the application of an electric current on the ab-plane in the paramagnetic insulating (PMI) state of (La0.4Pr0.6)(1.2)Sr1.8Mn2O7. A colossal electroresistance effect attaining -95% is observed at lower temperatures. A colossal magnetoresistive step appears near 5 T at low temperatures below 10 K, accompanied by an ultrasharp width of the insulator-metal transition. Injection of higher currents to the crystal and magnetic field cooling process cause a disappearance of the steplike transition. These findings have a close relationship with the presence of the short-range charge-ordered clusters pinned within the PMI matrix of the crystal studied.

DOI： 10.1063/1.3095598

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATL INST MATERIALS SCIENCE  

A system was developed measuring x-ray powder diffraction in high magnetic fields up to 5 T and at temperatures from 283 to 473 K. The stability of the temperature is within 1K over 6 h. In order to examine the ability of the system, the high-field x-ray diffraction measurements were carried out for Si and a Ni-based ferromagnetic shape-memory alloy. The results show that the x-ray powder diffraction measurements in high magnetic fields and at high temperatures are useful for materials research.

DOI： 10.1088/1468-6996/10/1/014612

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Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS  

X-ray powder diffraction, magnetization measurements, and differential thermal analysis (DTA) of polycrystalline MnBi were carried out in zero magnetic field as will as in magnetic fields of up to 14 T and in the temperatures range of 300-773 K, in order to investigate magnetic phase transition. In zero magnetic field, a magnetic phase transition from ferromagnetic to paramagnetic state is exhibited at temperature (T-t) of 628 K, accompanied by decomposition. With increasing magnetic field up to 14 T, T-t increases linearly with the rate of 2 KT-1. A metamagnetic transition between the paramagnetic and field-induced ferromagnetic states was observed just above T-t The exothermic and endothermic peaks were detected in the magnetic field dependence of DTA signals in the interval of 626-623 K, which relates to the metamagnetic transition. The obtained results are discussed on the basis of a mean field theory.

DOI： 10.2320/jinstmet.73.40

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOP PUBLISHING LTD  

We report the pressure effect on a steplike magnetostriction of single crystalline (La0.4Pr0.6)(1.2)Sr(1.8)Mb(2)O(7) bilayered manganite, for our understandings of the ultrasharp nature of the field-induced first-order transition from a paramagnetic insulator and to a ferromagnetic metal phase. Application of pressure suppresses a steplike transformation and causes a broad change in the magnetostriction. A delocalization of carriers is promoted with the applied pressure, resulting in the suppressed steplike behaviour. The steplike behaviour observed is closely related to the existence of localized carriers.

DOI： 10.1088/1742-6596/150/4/042121

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOP PUBLISHING LTD  

Rare earth sesquisulfides alpha-Tb2S3 and alpha-Dy2S3 possess orthorhombic crystal structure having two independent rare earth sites. High field magnetization processes for single crystals of these compounds have been investigated up to mu H-0 = 18 T. Some step-like transitions have been observed in both compounds. The magnetization of alpha-Tb2S3 single crystal under the field along the b-axis at T = 1.4 K shows a steep increase of about 4.5 mu(B), which corresponds to a half of full saturation moment of free Tb3+, at mu H-0 = 2.2 T. It is considered that the reorientation of Tb3+ moments on only one Tb site into a ferromagnetic arrangement occurs. When the magnetic field is perpendicular to the b-axis, one-step transition at mu H-0 = 0.7 T for H parallel to c and two-step transitions at 0.7 and 1.2 T for H parallel to a are observed. As for alpha-Dy2S3, the magnetization curve at T = 1.5 K shows two-step transitions at 1.3 and 1.6 T (H parallel to b), three or four dull steps (H parallel to a or c). The total height of two steps in the M-H curve for H parallel to b corresponds to a half of full Dy3+ moment.

DOI： 10.1088/1742-6596/150/4/042027

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOP PUBLISHING LTD  

The positive hyperfine field at Co nucleus in a Heusler alloy Co2TiGa is discussed to be not dominated by the orbital hyperfine field from a quite different point of view from former studies. Field-induced-moment nuclear coupling for Co-59 via spin-orbit interaction on Co atom in Co2TiGa is discussed to be small from the observed high-field shift of the NMR of Co-59 in the ferromagnetic state of only +0.83 % in contrast to the case of CoCl2 center dot 2H(2)O with +29%.

DOI： 10.1088/1742-6596/150/4/042037

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOP PUBLISHING LTD  

We have performed the specific heat and the electrical resistivity measurements under high magnetic fields for Heusler compounds Ru2CrGe and Ru2CrSn. We found that the electrical resistivity for Ru2CrGe shows an upturn in the vicinity of 130 K and changes a metallic to a semiconducting-like behavior with decreasing temperature. By applying magnetic field, a negative magnetoresistance was observed below 200 K. On the other hand, the electrical resistivity for Ru2CrSn shows a semimetallic-like behavior. The results of the electrical resistivity in Ru2CrGe suggest that the compound has a gap-like structure in the electronic structure at the Fermi level. Moreover, it was found that another phase transition occurs in Ru2CrGe and Ru2CrSn, in addition to the magnetic transition.

DOI： 10.1088/1742-6596/150/4/042153

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

The magnetostriction and magnetoresistance associated with the field-induced and spontaneous first-order antiferro-ferromagnetic (AF-F) phase transitions have been studied for quasi-single-crystalline samples of La(0.25)Sm(0.75)Mn(2)Si(2), La(0.25)Y(0.75)Mn(2)Si(2) and La(0.27)Y(0.73)Mn(2)Si(2) compounds with natural layered ThCr(2)Si(2)-type structure. It was found that both the spontaneous and field-induced AF-F transitions are accompanied by a large volume magnetostriction Delta V/V approximate to 2 x 10(-3) and anisotropic linear changes of the lattice parameters Delta a/a approximate to 1.6 x 10(-3), Delta c/c approximate to -0.75 x 10(-3). The field-induced AF-F magnetic phase transition has been observed in magnetic fields applied both along the c-axis and in the basal plane, and the magnetostriction value is virtually independent of the direction of applied field. It has been found also that the magnetoresistance is positive in these compounds (the value of the electrical resistance in the ferromagnetic state is higher than that in the antiferromagnetic state) for the fields applied both along the c-axis and in the basal plane. The value of the magnetoresistance observed along the c-axis is 30 times as high as that in the basal plane. The obtained results indicate that the electronic band structure changes are likely responsible for the AF-F magnetic phase transitions observed in the RMn(2)X(2) compounds.

DOI： 10.1088/0953-8984/20/44/445219

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

We report the effect of pressure on the steplike magnetostriction of single crystalline bilayered manganite (La(0.4)Pr(0.6))(1.2)Sr(1.8)Mn(2)O(7), for our understanding of the ultrasharp nature of the field-induced first-order transition from a paramagnetic insulator to a ferromagnetic metal phase. The application of pressure suppresses a steplike transformation and causes a broad change in the magnetostriction. The injection of an electric current to the crystal also weakens the steplike variation in both the magnetostriction and magnetoresistance. The stabilization of ferromagnetic interaction or the delocalization of charge carriers is promoted with the applied pressure or applied current, resulting in the suppressed steplike behavior. Our findings suggest that the step phenomenon is closely related to the existence of localized carriers such as the short-range charge-orbital-ordered clusters.

DOI： 10.1103/PhysRevB.78.132411

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

We report the electric conductivity of three-dimensional (3D) nanoporous gold at low temperatures and in strong magnetic fields. It was found that topologically disordered 3D nanoporosity leads to extremely low magnetoresistance and anomalous temperature dependence as the characteristic length of nanoporous gold is tuned to be similar to 14 nm. This study underscores the importance of 3D topology of a nanostructure on electronic transport properties and has implications in manipulating electron transport by tailoring 3D nanostructures.

DOI： 10.1103/PhysRevLett.101.166601

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Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

The concentration evolution of crystal structure, magnetic moment and anisotropy constants in U-2(Fe1-xNix)(13.6)Si-3.4 investigated on single crystals grown by the Czochralski method is found to be similar to that in the previously studied U-2(Fe1-xNix)(13.6)Si-3.4 system, only the Ni solubility is limited by x = 0.3 in difference with unlimited Co solubility. (c) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2007.06.086

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

The magnetostructural phase transformation and shape memory effect (SME) of Fe-added Ni(2)MnGa films were investigated. The free-standing films were heat-treated at 1073 K for 3.6 ks and constraint-aged (CA) at various conditions (473 similar to 723 K, 0 similar to 14.4 ks) to make the two-way SME. The reversible two-way SME by the temperature change was confirmed through the martensitic transformation (MT) and its reversion. The gradient of strain-temperature curve, the effective recovery strain and the width of thermal hysteresis were dependent on the CA conditions. The magnetic field (MF) induced structural phase transformation was evaluated by an XRD apparatus in high MF up to 5 T. It was confirmed that the martensitic phase was stabilized by the MF. Furthermore, the SME by the MF was observed around MT temperature on cooling process for the CA film. It was concluded that the MF induced SME appeared by the induction of the MT with MF.

DOI： 10.1140/epjst/e2008-00672-4

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High-field electron spin resonance (ESR) measurements of single crystals of (CH3)(2)NH2CuCl3 (DMACuCl(3)) have been performed in the frequency range of 50 to 550 GHz in the paramagnetic region. In addition to the electron paramagnetic resonance, we have observed four ESR modes omega(1), omega(2), omega(3), and omega(4). The modes omega(2) and omega(3) have a frequency gap of 325 GHz (15.6 K), while the mode omega(1) has a gap of 420 GHz (20 K) at 0 T. The modes omega(2) and omega(3) are attributed to the transitions between the singlet and the triplet of the antiferromagnetic (AF) dimer. We found that the large spin-gap for the AF dimer still remains at the critical field B-c2 = 3.5 T determined by magnetization and specific heat measurements.

DOI： 10.1143/JPSJ.76.113704

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The Sm-based filled skutterudite phosphides SmT4P12 (T = Fe, Ru, Os) have been studied by P-31-NMR (nuclear magnetic resonance) and mu SR (muon spin relaxation). The ferromagnetic order and the heavy fermion behavior in SmFe4P12 and the anti ferromagnetic order in SmOs4P12 were confirmed by P-31-NMR and mu SR. In SmRu4P12, a successive anomaly around the metal-insulator transition temperature and around the Neel temperature was observed by 31P-NMR in high applied magnetic fields. The mu SR results of SmRu4P12 indicate the magnetic order below the metal-insulator transition temperature, which supports the existence of the octupolar order in SmRu4P12. (c) 2007 Published by Elsevier Ltd.

DOI： 10.1016/j.jpcs.2007.08.033

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Field and temperature dependencies of the magnetization measured along the principal axes of a U2Co15Si2 single crystal show that this compound is a ferromagnet with a spontaneous magnetic moment of 14.8 mu(B) per formula unit (at 4.2 K), located in the basal plane of the hexagonal crystal structure. A strong easy-plane magnetic anisotropy (K-1 = -0.97 MJ m(-3) at 4.2 K) is attributed to the U sublattice because Lu2Co15Si2 exhibits easy-axis anisotropy with K-1 = 0.42 MJ m(-3). The easy-plane anisotropy of U2Co15Si2 transforms to a cone of easy axes above 270 K. The magnetization vector approaches the c-axis at 350 K, and the compound has easy c-axis anisotropy up to the Curie temperature T-C = 601 K. (C) 2007 Published by Elsevier B.V.

DOI： 10.1016/j.jmmm.2007.03.006

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Substitution of Y for U in the itinerant 5f-electron metamagnet, UCoAl, transforms the system to a ferromagnetic state. Application of external hydrostatic pressure above 0.3 GPa suppresses the ferromagnetism and restores the "UCoAl-type" metamagnetism back. However, the metamagnetic transition becomes of the second order instead of the first order one in parent UCoAl. This is attributed to enhancement of fluctuations of the U magnetic moment upon dilution of the U sublattice. (C) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2006.09.111

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS  

Magnetization measurements of polycrystalline MnBi were carried out in magnetic fields up to 10 T and in the temperature range from 300 to 773 K, in order to clarify the magnetic properties under high magnetic fields and high temperature. The magnetic phase transition temperature (T-c) at a zero magnetic field is 633 K, which almost linearly increases by 2.3 KT-1 with increasing fields up to 10 T. Furthermore, a metamagnetic transition was observed just above T, indicating that the phase transition is first order. The magnetic entropy change is estimated to be 14 J kg(-1) K-1 for 2 T at T-c using Clausius-Clapayron's equation, which is almost constant for magnetic fields up to 10 T.

DOI： 10.2320/jinstmet.71.489

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMERICAN PHYSICAL SOC  

We report a steplike lattice transformation of single crystalline (La0.4Pr0.6)(1.2)Sr1.8Mn2O7 bilayered manganite accompanied by both magnetization and magnetoresistive jumps, and examine the ultrasharp nature of the field-induced first-order transition from a paramagnetic insulator to a ferromagnetic metal phase accompanied by a huge decrease in resistance. Our findings support that the abrupt magnetostriction is closely related to an orbital frustration existing in the inhomogeneous paramagnetic insulating phase rather than a martensitic scenario between competing two phases.

DOI： 10.1103/PhysRevLett.98.267204

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

UGe2 is a ferromagnetic heavy-fermion (HF) superconductor, which provides superconductivity under pressure in the range of 1.0 to 1.5 GPa. In this paper, we conducted detailed magnetization experiments up to 27 T and at atmospheric pressure. Magnetization along the a-axis indicates typical ferromagnetic property. On the other hand, magnetization along the b-axis is quite a bit smaller than that of the easy a-axis. The magnetocrystalline anisotropy constant is the same as the rare earth ferromagnet Nd2Fe17, which indicates that UGe2 is a highly anisotropic ferromagnet.

DOI： 10.1088/0031-8949/75/4/030

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

For CuGeO3 single crystals doped with 1% of Fe, the quantum critical behavior in a wide temperature range 1-40 K is reported. The critical exponents for susceptibility along different crystallographic axes are determined: alpha = 0.34 (B parallel to a and B parallel to c) and alpha = 0.31 (B parallel to b). The description of the temperature dependencies of the line width and g-factor could be obtained in the Oshikawa-Affleck theory assuming that staggered component of the magnetic moment is located predominantly along b-axis. Possible arguments favoring the competition between effects of the staggered field and antiferromagnetic ordering are provided.

DOI： 10.1007/s10948-006-0214-3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMERICAN PHYSICAL SOC  

We have studied the pressure effect on magnetostriction, both in the ab plane and along the c axis of a (La, Pr)(1.2)Sr1.8Mn2O7 bilayered manganite single crystal over the temperature region where the field-induced ferromagnetic metal (FMM) transition takes place. For comparison, we have also examined the pressure dependence of magnetization curves at the corresponding temperatures. The applied pressure reduces the critical field of the FMM transition and it enhances the remanent magnetostriction. An anomalous pressure effect on the remanent lattice relaxation is observed and is similar to the pressure effect on the remanent magnetization along the c axis. These findings are understood from the viewpoint that the double-exchange interaction-driven FMM state is strengthened by the application of pressure.

DOI： 10.1103/PhysRevB.75.014427

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

Lu2Fe17 is a ferromagnet below T-C similar to 140 K and antiferromagnet up to T-N = 275 K. Hydrogen absorption leads to a stabilization of the ferromagnetism over the whole range of magnetic order and to an increase of the ordering temperature up to T-C=354 K in Lu2Fe17H. The external pressure compensates the lattice expansion upon hydrogenation, and a reentrance of antiferromagnetism is observed.

DOI： 10.1143/JPSJS.76SA.82

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMERICAN PHYSICAL SOC  

Magnetooptical measurements have been performed on the organic conductor beta(')-(BEDT-TTF)(TCNQ) (x=0 salt), and a related compound, beta(')-(BEDT-TTF)(TCNQ)(0.95)(F1-TCNQ)(0.05) (x=0.05 salt), to investigate their low-temperature Fermi surfaces (FSs). Although the room-temperature FS of both salts can be considered the same, our results indicate that the low-temperature FSs are completely different from each other. In the x=0 salt, the low-temperature FS consists of two very anisotropic quasi-two-dimensional (Q2D) FSs. Cross-sectional areas of anisotropic Q2D-FSs are very small, and correspond to 1-2 % of the first Brillouin zone at room temperature. On the other hand, in the x=0.05 salt, only a pair of quasi-one-dimensional FSs exist at low temperature. Compared with the band calculation of x=0 salt, this Q1D-FS originates from the BEDT-TTF conducting layers. This result indicates that the two hump-like anomalies in the temperature dependence of resistivity at 80 and 20 K, which are observed only in the x=0 salt, are related to the nesting of BEDT-TTF Q1D-FS. Hence, it is considered that anisotropic Q2D-FS pockets observed in the x=0 salt are generated by the imperfect nesting of Q1D-FS, and the density wave state may be formed in the x=0 salt at low temperatures.

DOI： 10.1103/PhysRevB.75.045126

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

Substitution of Y for U in the itinerant 5f-electron metamagnet UCoAl transforms the system to a ferromagnetic ground state. Application of external hydrostatic pressure above 0.3 GPa suppresses the ferromagnetism and restores the "UCoAl-type" metamagnetism. However, the metamagnetic transition becomes of the second-order type instead of the first-order one for the parent UCoAl.

DOI： 10.1143/JPSJS.76SA.43

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The P-31-NMR (nuclear magnetic resonance) measurements of the filled skutterudite SmRu4P12 have been carried out in several applied magnetic fields. The line width of the P-31-NMR spectrum rapidly increases below the metal-insulator transition temperature T-MI, which indicates the appearance of an internal field below the temperature. Though no distinct anomaly was observed below T-MI in low fields, a complicated structure was observed between the Neel temperature T-N and T-MI (T-N &lt; T-MI) above 70 kOe. The spin-lattice relaxation rate l/T-1 is almost independent of temperature above T-MI, and rapidly decreases below T-MI. The l/(T1) in low fields decreases monotonously, whereas the strong suppression of l/(T1) occurs between T-N and T-MI above 70 kOe. The structure of the spectra and the suppression of l/T-1 become apparent with increasing field.

DOI： 10.1143/JPSJ.75.124712

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A discontinuity in the temperature dependence of the lattice parameters while preserving the crystal symmetry was observed for TbPdAl, TbNiAl and TbPd0.9Ni0.1Al. We associate this result with the previously reported step-like change in the concentration dependence of lattice parameters in RE(Ni1-xCux)Al pseudo-ternary compounds. Our results corroborate the scenario for the RTX compounds with the ZrNiAl-type structure based on existence of a narrow interval of forbidden c/a values. For TbPdAl, TbNiAl and TbPd0.9Ni0.1Al we observed also a certain temperature interval of coexistence of two ZrNiAl-type phases characterized by two distinctly different c/a values. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2006.01.437

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

X-Ray powder diffraction method is used to investigate the effect of magnetic ordering and external magnetic field on crystal structure of Laves phase intermetallic compound ErCo2. The diffraction patterns were recorded at temperatures from 300 K down to 8.5 K in magnetic field up to 5 T. Distortion of the room-temperature cubic structure was found in magnetically ordered state below 32 K. The symmetry at low temperature is rhombohedral in agreement with literature results. Or lower symmetry than it. However the symmetry of the unit cell increases to cubic in external magnetic field of 5 T. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2006.01.514

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Language：English   Publisher：JAPAN INST METALS  

DOI： 10.1113/jphysiol.2006.114231

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER/PLENUM PUBLISHERS  

The detailed topology of the Fermi surface of the quasi-one-dimensional conductor (DMET)(2)I-3 was investigated by the magnetooptical measurements. A pair of planar Fermi surface which has higher corrugations of Fourier components was observed. This result seems to suggest that the metallic state of this salt is stabilized by the higher corrugations of the Fermi surface.

DOI： 10.1007/s10909-006-9159-y

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

We have studied the magnetic properties of Ce(Fe1 xCox)(2) with x = 0 and 0.05 by magnetization measurements under high pressure. In both compound, the remarkable suppression of the magnetization is observed below T* in the ferromagnetic (FM) state under 1.2 GPa. T* shifts to lower temperature with increasing the magnetic field, and the extrapolated value to the zero magnetic field is estimated to be 95 and 123 K. These high pressure and magnetic field effects are probably due to the enhancement and the suppression of the AFM spin fluctuation, respectively. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2005.04.057

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

A series of nanocomposite thin films, composed of alpha-Fe and c-axis oriented SmFe12 phases, has been synthesized by rf magnetron sputtering onto heated glass substrates. The volume fraction of alpha-Fe, V-Fe, in the obtained films ranges from 5% to 85%. According to the Rietveld analysis of X-ray diffraction patterns, the c-axis of each SmFe12 grain was estimated to locate within a cone with its symmetry axis being normal to the film plane and with the cone angle of 7 degrees. For samples with VFe &lt; 30%, the demagnetization curves with fields applied normal to the film plane have exhibited a good squareness. In small VF, films, the coercivity H, increased with increasing V-Fe took a maximum for VFe similar to 25%, and then decreased. In the reference system of randomly aligned SmFe12/alpha-Fe films, on the other hand, we confirmed that H-c decreased monotonically with increasing V-Fe. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2005.04.108

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DOI： 10.1109/INTMAG.2006.374945

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOP PUBLISHING LTD  

Measurements of high-field magnetization up to 18 T, magnetic susceptibility and specific heat have been performed on a tetragonal NdRh2Ge2 single crystal and polycrystalline sample. From the temperature dependences of magnetic susceptibilities, this compound shows an antiferromagnetic behaviour with Neel temperature of 50 K. Another magnetic transition is observed at 37 K. At low temperatures, a multi-step metamagnetic behaviour is observed along the easy c-axis and a strong magnetic anisotropy is seen. The saturation magnetic moment is estimated to be 2.76 mu(B)/f.u.. There are five magnetic phases below the induced ferromagnetic phase in the H-T magnetic phase diagram. To discuss the magnetic behaviours, the CEF analysis has been made.

DOI： 10.1088/1/1742-6596/51/1/012

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IOP PUBLISHING LTD  

We have conducted low- and high-field magnetization measurements and neutron diffraction experiments on NdxEr1-xMn6Sn6 alloys (0 &lt;= x &lt;= 0.5) with hexagonal MgFe6Ge6 type structure. The alloy with x = 0.1 shows a complex helical antiferromagnetism with the magnetic moments rotating in the c plane below the Curie temperature T-C = 340 K, and a ferrimagnetism below the temperature T-t = 100 K. In the ferrimagnetic state, the magnetic moments mu(Mn) and mu(Nd) are parallel to each other, and antiparallel to mu(Er). The alloy with x = 0.4 shows also a similar ferrimagnetic structure below the Curie temperature T-C = 360 K. It is likely that the each magnetic moments are keep a constant values of mu(Mn) = 2.3 mu(B)/Mn atom, mu(Nd) = 3 mu(B)/Nd atom and mu(Er) = 9 mu(B)/Nd atom at 10 K in the whole composition (0 &lt; x &lt;= 0.5). The ferrimagnetic arrangements for the alloys with 0.2 &lt;= x &lt;= 0.5 are not almost disturbed by magnetic field up to 26 T at 4.2 K.

DOI： 10.1088/1/1742-6596/51/1/008

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Substitution of Y for U in the itinerant 5f-electron metamagnet, UCoAl, transforms the system to a ferromagnetic state. Application of external hydrostatic pressure above 0.3GPa suppresses the spontaneous ferromagnetism and restores the paramagnetism with field-induced transition to ferromagnetic state. However, the transition becomes of the second order instead of the first-order one in parent UCoAl. © 2006 Taylor &amp
Francis.

DOI： 10.1080/08957950601103973

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

We have performed specific heat measurements of a high-quality polycrystalline sample of CuV2S4. Two anomalies associated with charge density wave (CDW) transitions are clearly observed at T-t1 = 92 K and T-t2h = 58 K. The anomalies at T-t1 and T-t2h show lambda-type and spike-shaped behavior, indicating second and first order phase transitions, respectively. The electronic specific heat coefficient gamma and the Debye temperature Theta(D) are estimated to be 36 mJ/moIK(2) and 347 K, respectively. gamma of CuV2S4 is much larger than that of CuTi2S4, whereas CuTi2S4 exhibits a CDW gap at low temperature. This enhancement of gamma is probably attributed not only to the electron-phonon interaction but also to electron-electron interactions.

DOI： 10.1063/1.2355192

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

We have performed magnetooptical measurements of beta ''-(BEDT-TTF)(TCNQ) using a cavity perturbation technique with a millimeter vector network analyzer (MVNA) and a 14 T superconducting magnet at IMR, Tohoku University. The results of ADMRO and SdH measurements at low temperatures are not consistent with the band calculation result. Therefore, we are interested in Fermi surfaces at low temperatures and have performed magnetooptical measurements of beta ''-(BEDT-TTF)(TCNQ). Although the band calculation and ADMRO results suggest the existence of Q1D FS, our results suggest the existence of Q2D FS only. From the results of magnetooptical measurements, we discuss the FS topology of this system at low temperatures.

DOI： 10.1016/j.synthmet.2005.07.308

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN INST METALS  

We performed the powder X-ray diffraction measurements in magnetic fields up to 5T for Gd-5(Ge1.95Fe0.05)Si-2 and Gd-5(Ge(1.8)Fc(0.2))Si-2-With heating from 8 K, the matrix of Gd-5(Ge1.95Fe0.05)Si-2 clearly shows a structural transition from an orthorhombic to a monoclinic structure at the Curie temperature (Tc = 276 K). On the other hand, the matrix of Gd-5(Ge1.8Fe0.2)Si-2 with the orthorhombic structure in the ferromagnetic state shows two-phases co-existence of the orthorhombic and the monoclinic structures above Tc = 303 K, indicating that a small amount of the matrix participates in the transformation. For both samples, the monoclinic structure is suppressed but the orthorhombic structure is enhanced just above Tc by applying a magnetic field, which closely relates to the magnetization process.

DOI： 10.2320/matertrans.46.2011

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

A rotational resonant cavity equipped with a millimeter vector network analyzer (MVNA) and a 14T solenoid type superconducting magnet has been developed. The available frequency range is about 50-100GHz. The temperature can decrease to 1.5 K. The cavity can rotate within the precision of one degree. As an example of the application of the new resonant cavity, we have performed detailed magnetooptical measurements of an organic conductor to estimate the Fermi surface topology. The Fermi surface of the quasi-one-dimensional conductor (DMET)(2)I(3) is discussed.

DOI： 10.1143/JJAP.44.4930

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A series of Nd2Fe14B/&alpha;-Fe nanocomposite thin films, in which the crystallites of the Nd2Fe14B phase are well-oriented, has been synthesized by RF magnetron sputtering onto heated glass substrates. Magnetization curves exhibited single-phase-like hysteresis loops, suggesting that the two phases are firmly exchange-coupled. By comparing the observed magnetization curves with the micromagnetic calculations, we have estimated the intergrain exchange-coupling constants. &COPY; 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2004.11.407

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

The high-field X-ray diffraction measurement of a re-entrant ferromagnet SmMn2Ge2 with a tetragonal structure was carried out. The unit cell volume contracts by approximately 0.3% in the antiferromagnetic (AFM) state, compared with that of the ferromagnetic (FM) state. In the AFM state, the structural distortion recovers due to a high magnetic field, accompanied by the metamagnetic transition from the AFM state to the forced FM state.

DOI： 10.1143/JJAP.44.1258

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

Submillimeter and millimeter wave electron spin resonance (ESR) measurements of BaCu2(Si1-xGex)(2)O-7, which is a mixed system of an S=1/2 one-dimensional Heisenberg antiferromagnet with the Dzyaloshinskii-Moriya interaction, have been performed to investigate the limitations of the Oshikawa-Affleck theory for the ESR of an S=1/2 one-dimensional Heisenberg antiferromagnet with a staggered field. The magnetic field dependence of the linewidth and the field induced energy gap will be discussed in connection with the Oshikawa-Affleck theory.

DOI： 10.1143/JPSJ.74.80

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

The EPR spectra along different crystallographic axes for single crystals of CuGeO3 containing 1% of Fe impurity have been studied in the frequency range 60-360 GHz at temperatures 0.5-30 K. The analysis based on the Oshikawa-Affleck theory suggests that the temperature dependences of the line width and g-factor are formed as a result of the competition between interchain antiferromagnetic interactions and staggered Zeeman energy. It is found that staggered magnetic moments in CuGeO3:Fe are located predominantly along b axis.

DOI： 10.1143/PTPS.159.387

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMERICAN PHYSICAL SOC  

The transition between the antiferromagnetic (AF) and the ferromagnetic (F) states has been investigated with regard to the magnetovolume effect and the spin-fluctuation characteristics in La(FexAl1-x)(13) compounds. The volume V and amplitude of the local magnetic moment M-loc are different between the AF and F states. In the AF state, the field-induced first-order AF-F transition appears and the transition proceeds with two steps in higher Fe concentration regions. The complex temperature dependence of the AF-F transition field is explained by the contribution from both the magnetic and elastic energies caused by the significant temperature variation of amplitude of M-loc. For the two-step transitions, the spin-floplike transition and the increase in amplitude of M-loc occur at the first- and second-step transitions, respectively. In other words, both the localized moment and the itinerant-electron characteristics are concurrently observed.

DOI： 10.1103/PhysRevB.70.214405

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

We have developed a new magneto-optical measurement system with a rotational cavity. It consists of a millimeter vector network analyzer and a 15T solenoid type superconducting magnet and it can go down to 1.5 K. The rotational cavity can be used in the transmission configuration and the rotation can be performed up to almost 360 degrees in 1 degree precision. We will show the magneto-optical measurement results of, beta ''-(BEDT-TTF)(TCNQ) using our new system. We observe the quasi-two-dimensional periodic orbit resonance (POR) in beta ''-(BEDT-TTF)(TCNQ). The Fermi surfaces of this system will be discussed.

DOI： 10.1142/S0217979204027487

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

We have studied the magnetic properties of Ce(Fe1-xCox)(2) with x less than or equal to 0.1 by magnetization measurements under high pressures up to 1.2 GPa. In pure CeFe2, the Curie temperature T-C decreases, and the saturation magnetization M-s is suppressed by applying pressure. In Co substitution compounds, the transition temperature T-A from the ferromagnetic (FM) to the antiferromagnetic (AFM) states and the metamagnetic transition field B-c increase with increasing pressure, while T-C and the magnetization of the spontaneous and field-induced FM states decrease. The obtained results indicate that the AFM state becomes stable by the lattice contraction.

DOI： 10.1143/JPSJ.73.1982

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

We are now developing a 30 T hybrid magnet utilizing a cryocooler-cooled superconducting magnet wound with highly strengthened (Nb, Ti)(3)Sn. Diameter of the room temperature bore of the superconducting magnet is 360 mm and it generates 11.1 T. Water cooled resistive insert magnet generates 18.9 T, thus the hybrid magnet generates a central field of 30.0 T. The (Nb, Ti)(3)Sn multifilamentary wires are strengthened by Cu/NbTi composite which volume ratio in conductor is about 35%. The reinforcing Cu/NbTi composite changes to CuTi intermetallic compounds during heat treatment for reaction of (Nb, Ti)(3)Sn phase formation. The Nb3Sn coil with inner diameter of 400 mm will be fabricated by wind and react method with Cu/NbTi reinforced (Nb, Ti)(3)Sn wires. The innermost section of Nb3Sn coil is wound with a wire which diameter is 1.85 mm and next second section is wound with a wire diameter of 1.8 mm. The Nb3Sn coil is operated at 303 A and generates 5.8 T. The NbTi coil is wound with NbTi wires of 2.0 mm and 1.6 mm diameters. The NbTi coil generates 5.3 T at an operating current of 350 A. The maximum hoop stress is under 220 MPa for Nb3Sn coil and 200 MPa for NbTi coil.

DOI： 10.1109/TASC.2004.829672

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Magnetovolume effect due to the itinerant-electron metamagnetic (IEM) transition in La(Fe0.88Si0.12)(13) has been investigated by x-ray diffraction measurements in high magnetic fields. No crystal structure change was confirmed after the IEM transition. The relative change in the lattice constant measured perpendicular to the magnetic field direction is similar to the longitudinal linear magnetostriction, and hence the volume change due to the IEM transition is isotropic. The volume change in both the ferromagnetic and the paramagnetic states is proportional to the square of the magnetization, though the magnetovolume coupling constant in the former is smaller than that in the latter. (C) 2004 American Institute of Physics.

DOI： 10.1063/1.1667455

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We have performed the high-field ESR of the one-dimensional BaCu2(Si1-xGex)(2)O-7 (x = 0.65) antiferromagnet at 0.5 and 1.8 Kin the wider frequency and magnetic field region (40-500 GHz, up to 30 T), and found the breather excitation predicted by the Oshikawa-Affleck (OA) theory. The observed field-induced gap for Bparallel toc (chain direction) shows the B-2/3 dependence suggested by the OA theory, and the dependence is weak for the other directions which is consistent with the anisotropy of the Dzyaloshinsky-Moriya interaction. The results will be also discussed in connection with the breather excitation observed in Cu-benzoate. (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2003.12.547

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We have performed the magnetization and X-ray diffraction measurements on Mn3Ga1-xAlxC (0 &lt;= x &lt;= 0.1) with a perovskite-type structure in the temperature T range from 5 to 400 K to investigate the behavior of the complicated magnetic phase transitions. The obtained results suggest that the crystallographic character is closely correlated to the magnetic properties. The new magnetic phase diagram of this system is presented, which indicates the two-phases coexistence in Mn3Ga1-xAlxC at lower temperature. (C) 2003 Elsevier B. V. All rights reserved.

DOI： 10.1016/j.jmmm.2003.11.312

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

(n-C3H7)(4)N[(FeFeIII)-Fe-II(dto)(3)] shows a new type of first order phase transition called chare-transfer phase transition around 120 K. where the charge transfer between Fe-II and Fe-III occurs reversibly. Recently, we have succeeded in obtaining single crystals of the title complex and determined the crystal Structure at room temperature. Crystal data: space group P6(3), a = 10.0618(5) Angstrom. c = 16.0424(7) Angstrom. V = 1406.54(12)Angstrom, Z = 2. Moreover. we have investigated the structural transition caused by the charge-transfer phase transition by means of powder X-ray diffraction measurement. When the temperature is decreased. the a-axis. which corresponds to the hexagonal ring size in two-dimensional honeycomb network structure of [Fe-II Fe-III(dto)(3)](infinity). contracts by 0.1 Angstrom at the charge-transfer transition temperature (T-CT) while the c-axis. perpendicular to the honeycomb network layer. elongates by 0.1 Angstrom at T-CT. Consequently, when the temperature is decreased, the unit cell volume decreases without noticeable anomaly around T-CT, which is responsible for the quite sniall vibrational contribution to the entropy change. compared with usual spin crossover transition. Thus, the charge-transfer phase transition around 120 K for (n-C3H7)(4)N[Fe-II Fe-III(dto)(3)] is regarded as spin entropy driven phase transition. (C) 2004 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ssc.2004.02.034

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The temperature and magnetic field dependences of lattice parameter for Ce(Fe1-xCox)(2) with x = 0, 0.05 and 0.10 are examined by powder X-ray diffraction measurement. The strong correlation between structural phase and magnetic state in these compounds is discussed. (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2003.11.245

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The magnetic and structural properties of Ce(Fe0.9Co0.1)(2) with the C15 cubic Laves-phase structure have been studied by magnetization measurement in high magnetic fields under high pressures, and powder X-ray diffraction measurement in fields up to 5 T. The C15 cubic structure is distorted to rhombohedral symmetry accompanied with the magnetic phase transition from the ferromagnetic to the antiferromagnetic state, which recovered the C15 structure by applying the magnetic field. The antiferromagnetic phase is induced by the lattice contraction due to hydrostatic pressure. Obtained results suggest that the AFM correlation due to the Cc 4f-Fe 3d hybridization plays an important role on the structural and magnetic properties. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2004.01.047

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Magneto-optical measurements of a quasi-one-dimensional (q1D) organic superconductor (DMET)(2)I-3 has been performed by using a cavity perturbation technique. Several resonant absorption lines, which can be attributed to the q1D periodic orbit resonance (q1D POR), as well as the quite unusual high-order q1D POR coming from the corrugated Fermi surface (FS) in the interlayer direction were observed. Moreover, other harmonic resonances are also observed when the AC electric field is applied along the c*-axis. We will also show its estimated q1D FS from the data analysis where the estimated FS clearly shows why there is no spin-density-wave or charge-density-wave transition in (DMET)(2)I-3 despite having a q1D FS. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2004.01.112

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Magnetooptical measurements have been performed on beta"-(BEDT-TTF)(TCNQ) using the cavity perturbation techniques. beta"-(BEDT-TTF)(TCNQ) has very exotic Fermi surface (FS). Several harmonic resonances were observed at various angles. We consider these resonances as q1D-periodic orbit resonance. The obtained Fermi velocity and the scattering time are 4.4 x 10(4) m/s and 2.1 x 10(-11) s, respectively. When the magnetic field was rotated in the b*a-plane, the similar resonances are observed. According to these results, the FS topology of the system at low temperature is discussed. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2004.01.111

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

We have studied the magnetic and structural properties of Ce(Fe0.9Co0.1)(2) with the C15 cubic Laves-phase structure by low-temperature x-ray diffraction measurements in magnetic fields up to 5 T, and in the temperature range from 9 to 300 K. The C15 structure is distorted to rhombohedral symmetry at 90 K in zero magnetic field, accompanied with the magnetic phase transition from the ferromagnetic (FM) to the antiferromagnetic (AFM) states with decreasing temperature. In the AFM state, it is observed clearly that the rhombohedral distortion state recovers the C15 structure by applying magnetic field, accompanied with the metamagnetic transition from the AFM to the forced FM states with a hysteresis in the magnetization process.

DOI： 10.1143/JPSJ.73.676

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Institute of Metals (JIM)  

Structural transformation induced by magnetic fields on MnAs and MnAs 0.9Sb0.1 was investigated by the X-ray diffraction measurements in high magnetic fields up to 5T. The X-ray diffraction profiles at 319 K for MnAs showed a single phase of the orthorhombic MnP-type structure in zero field, and applying a magnetic field of 3 T caused an appearance of the hexagonal NiAs-type structure. On further increase of magnetic fields, the single phase with the hexagonal structure was confirmed above 3.5 T in a forced ferromagnetic state. The X-ray diffraction profiles at 295 K for MnAs 0.9Sb0.1 showed the hexagonal NiAs-type structure. However, the coexistence of two kinds of the NiAs-type structure with different lattice parameters was confirmed in the magnetic field of 2.5 T. The two phase coexistence was also confirmed in the temperature variation measurements in zero magnetic field. The lattice volume of the ferromagnetic phase was 1.1% larger than that of the paramagnetic phase. These results imply that the transition at TC for MnAs0.9Sb0.1 is of the first-order.

DOI： 10.2320/matertrans.45.311

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

We have developed a rotational resonant cavity equipped with the millimetre vector network analyser and the 14 T superconducting solenoid magnet. The measurement can be performed down to 1.6 K and the frequency range is about 50100 GHz. As an example of its application, the results of the precise angular dependence measurements of the quasi one dimensional organic conductor (DMET)(2)I-3 are presented.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

Cyclotron resonance (CR) measurements on high-quality single crystals of rare-earth monopnictides have been performed in the frequency range from 50 to 190 GHz. We have successfully observed CR signals for a strongly correlated electron system, CeSb, as well as other rare-earth monopnictides, LaSb and PrSb. We have also observed Doppler-shifted CR including nonlinear behaviour in the frequency-field diagrams.

DOI： 10.1088/0953-8984/15/28/333

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

Electron spin resonance (ESR) measurements on single crystals of GdX (X = P, As, Sb and Bi) have been performed in the temperature range from 50 to 1.7 K and in the frequency range from 50 to 109 GHz to obtain microscopic information on the magnetic properties. The results obtained indicate that GdX is an "easy-plane" antiferromagnet with the magnetic moment lying in the (111) plane below the Neel temperature. In addition, ESR affected by hyperfine interaction was observed in GdBi.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

An electron spin resonance (ESR) measurement system for use at ultralow temperatures using a He-3-He-4 dilution refrigerator has been developed down to 160 mK. As the first experiment, the ESR was measured on a quantum spin chain Cu benzoate, in which a field-induced gap was recently found. The evaluation of a new ESR mode, so-called breather mode, was found at the lowest temperatures. In the present work, we observed a smaller gap in Hparallel tob by suppressing of the thermal excitation. (C) 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4526(02)02433-X

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

An antiferromagnetic resonance in lambda-(BETS)(2)FeCl4 has been observed at 23-110 GHz in the antiferromagnetic insulating state. The frequency-field diagram, which is basically explained by a two-sublattice model, indicates that the spin system has a biaxial anisotropy and the a(*)-axis is close to the hard axis.

DOI： 10.1016/S0379-6779(02)00745-2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Magnetooptical measurements of quasi-one-dimensional organic conductor (DMET)(2)I-3 have been performed by using a cavity perturbation technique with Millimeter Vector Network Analyzer (MVNA). Several resonances are observed and these resonances disappear when the magnetic field is applied nearby the conducting b-axis. These resonances seem to come from the periodic modulation of group velocities of the carriers on the quasi-one-dimensional Fermi surface (q1D FS). However, these resonances show a different angular dependence with the Fermi traversal resonance (FTR) or quasi-one-dimensional periodic orbit resonance (q1D POR).

DOI： 10.1016/S0379-6779(02)00721-X

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Magneto-optical measurements of beta-(BEDT-TTF)(2)Aul(2), which has an isotropic two dimensional Fermi surface in the ab-plane, have been performed at 1.8 K by using cavity perturbation technique with steady magnetic field and mosaic transmission technique with pulsed magnetic field. A cyclotron resonance coming from the quasi two dimensional Fermi surface has been observed in both measurements for Hperpendicular toab-plane. Obtained effective mass was 0.9 m, and this result is smaller than the mass obtained by the Shubnikov-de Haas measurement, which suggests the existence of electron-electron interactions in the system.

DOI： 10.1016/S0379-6779(02)00718-X

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

DOI： 10.1143/JPSJ.72.767

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMERICAN PHYSICAL SOC  

From microwave cavity transmission measurements at 23-110 GHz on lambda-(BEDT-TSF)(2)FeCl4, we have observed an antiferromagnetic resonance (AFMR) in the antiferromagnetic insulating state below the metal-to-insulator transition temperature of T-MI=8.3 K. The frequency-field dependence is fundamentally reproduced with a two-sublattice model for a biaxial anisotropy. The easy axis is confirmed to be the direction tilted by 30degrees from c to b(*), and the hard axis is found to be close to a(*). The spin-flop field is identified to be 1.3 T through the frequency-field dependence for the easy axis. The AFMR is interpreted to be caused by spin waves excited on the pi spins, exclusively due to the large pi-pi exchange interaction estimated by theoretical calculations. The exchange field and anisotropy fields for pi spin systems at 1.2 K are evaluated to be H(E)similar to330 T, H(A)(1)similar to1.5x10(-3) T for the intermediate axis and H(A)(2)similar to5.0x10(-3) T for the hard axis, respectively.

DOI： 10.1103/PhysRevB.67.020408

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From microwave cavity transmission measurements at 23–110 GHz on (formula presented) we have observed an antiferromagnetic resonance (AFMR) in the antiferromagnetic insulating state below the metal-to-insulator transition temperature of (formula presented) The frequency-field dependence is fundamentally reproduced with a two-sublattice model for a biaxial anisotropy. The easy axis is confirmed to be the direction tilted by (formula presented) from c to (formula presented) and the hard axis is found to be close to (formula presented) The spin-flop field is identified to be 1.3 T through the frequency-field dependence for the easy axis. The AFMR is interpreted to be caused by spin waves excited on the (formula presented) spins, exclusively due to the large (formula presented) exchange interaction estimated by theoretical calculations. The exchange field and anisotropy fields for (formula presented) spin systems at 1.2 K are evaluated to be (formula presented) (formula presented) for the intermediate axis and (formula presented) T for the hard axis, respectively. © 2003 The American Physical Society.

DOI： 10.1103/PhysRevB.67.020408

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Physical Society of Japan  

Electron spin resonance (ESR) measurements on single crystals of GdX (X = P, As, Sb and Bi) have been performed in the temperature range from 50 to 1.7 K and in the frequency range from 50 to 109 GHz to obtain microscopic information on the magnetic properties. The results obtained indicate that GdX is an "easy-plane" antiferromagnet with the magnetic moment lying in the (111) plane below the Néel temperature. In addition, ESR affected by hyperfine interaction was observed in GdBi. © 2003 The Physical Society Japan.

DOI： 10.1143/JPSJS.72SB.145

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

For clarifying the role that the interstitial N atoms played on the microscopic scale for basic magnetism in R2Fe17N3, we determined the enhancements of Fe magnetic moments on the crystallographically different atomic sites and crystalline electric field parameter A, upon nitrogenation by neutron diffraction studies of the rhombohedral Y2Fe17 and Y2Fe17N3.1 and high-field magnetization measurements of single crystalline Nd2Fe17 and Nd2Fe17N3, respectively. The results obtained are compared with those estimated by the band structure calculation. For clarifying the coercivity mechanism in Sm2Fe17N3, we also examined the particle (powder) size and surface cleaning effects on the coercive field mu(0)H(e) for the Sm2Fe17N3 single crystal powder. The results indicate that mu(0)H(e) monotonically decreases with increasing the particle size, suggesting that the coercivity mechanism is of a nucleation type. When there are many nucleation sites on the surface of Sm2FeN3 powder before surface cleaning, the value of mu(0)H(e) is relatively small and reveals strong temperature dependence, while mu(0)H(e) is strongly enhanced by surface cleaning, leading to relatively weak temperature dependence. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0304-8853(01)01189-1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

An electron spin resonance (ESR) apparatus with a high sensitivity vector network analyzer has been developed for use at ultralow temperatures. The microwave frequency can be varied between 45 and 110 GHz. The resonant cavity was installed in a He-3-He-4 dilution refrigerator which provides ultralow temperatures down to 160 mK. In order to avoid the heating of the cavity and the sample by microwaves or heat leaks in the cryostat, attenuators and thermal anchors were placed at the most suitable positions. As the first experiment, the ESR was measured for a quantum spin chain Cu benzoate. The breather mode, which is a new ESR mode caused by a field induced gap, has been clearly observed at the lowest temperatures. (C) 2002 American Institute of Physics.

DOI： 10.1063/1.1448901

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

The cyclotron resonance is the best way to determine the effective masses of conductors and it is interesting to compare them with other effective masses determined by the de Haas oscillations. According to Kohn's theorem, they are not necessarily coincident with each other because an electron-electron correlation in the strongly correlated electron systems contributes to only the case of the de Haas oscillations. This argument has been studied in the case of organic conductors. On the other hand, it has been difficult to observe the cyclotron resonance absorption in rare-earth semimetals due to necessity of high frequency equipment, high magnetic field, very low temperature and high quality specimen. We have succeeded in observing cyclotron resonance in some rare-earth monopnictide compounds RX (R=rare earth atom, X=pnictgen atom) with NaCl type crystal structure and discussed the relationship between two kinds of masses of these materials. As reference materials, nonmagnetic LaSb and PrSb were also studied. In these cases, we have found new nonlinear resonance lines in addition to the normal cyclotron resonance whose resonance frequencies are linear with respect to magnetic field intensity. We ascribe this effect to the Doppler shift caused by coupling of cyclotron motion of carriers with the Alfven wave propagating in the material.

DOI： 10.1109/ICIMW.2002.1076051

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The cyclotron effective masses of rare earth monopnictides were determined. These masses were obtained by cyclotron resonance (CR) measurements in the frequency range between 56 GHz and 190 GHz in the temperature range between 50 K and 0.5 K. The experimental results on CR measurements for single crystals of rare earth compounds were presented using a vector network analyzer (AB millimeter) and a resonant cavity. In addition to normal cyclotron resonance, two anomalous absorption lines were observed for the high quality single crystal of LaSb.

DOI： 10.1016/S0022-3697(02)00053-7

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

An electron spin resonance (ESR) measurement system for use at ultralow temperatures using a He-3-He-4 dilution refrigerator has been developed. As the first experiment. the ESR was measured on a quantum spin chain Cu benzoate clown to 160 ml. in which a field-induced gap was recently found.((4)) The evaluation of a new ESR mode. the so-called breather mode, was found at the lowest temperatures. In the previous ESR down to 0.5 K, this mode was clearly found for H // c. in which the magnitude of the gap is largest. In the present work. the achievement of low temperatures enabled us to observe a smaller gap in H // b by suppressing the thermal excitation. The magnitude of the field-induced gap evaluated from the nonlinear field dependence of the mode shows good agreement with that determined by previous specific heat measurements.

DOI： 10.1143/JPSJ.70.2259

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Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

Thin-film magnets, composed of nanophase dispersed Nd2Fe14B and alpha -Fe have been synthesized by rf magnetron sputtering. With increasing alpha -Fe volume fraction V-Fe the saturation magnetization increased linearly, while the coercivity decreased. Ferromagnetic resonance measurements were made by using a high-frequency and high-field ESR apparatus, which exhibited two absorption peaks. A model calculation of the resonance field was made for a simplified hard/soft two-sublattice system to analyze these results. Estimated values of the exchange-coupling constant are in good agreement with those deduced from micromagnetic analysis of the magnetization curves.

DOI： 10.1109/20.951237

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Cyclotron resonances of quasi-two-dimensional organic conductor theta-(BEDT-TTF)(2)I-3 have been observed by using Millimeter Vector Network Analyzer (MVNA), V- and W-Band Cavity at 0.5K. Two resonances are observed, and the mode coupling in the cavity suggests that the resonances are cyclotron resonances. Obtained effective masses 1.03m(o) and 2.14m(o) are assigned to be alpha and beta orbits, respectively.

DOI： 10.1016/S0379-6779(00)00711-6

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Magnetization measurements have been performed on single-phase Ce2Fe17 with a rhombohedral structure under high pressures up to 1.2 GPa and in magnetic fields B up to 17T to clarify the pressure effect on the magnetic phase transitions. At 0.8 GPa, we observed at least seven magnetic phases in the B-T plane. The results obtained indicate that the hybridization between the Fe 3d- and Ce 4f-electron states plays an important role for the magnetic properties of Ce2Fe17. (C) 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4526(00)00634-7

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)