Faculty Profiles - SHIGETA Iduru

Masakazu Ito, Toru Hisamatsu, Tsugumi Rokkaku, Osamu Murayama, Iduru Shigeta, Masahiko Hiroi . Thermodynamic and transport properties of Ru2-x Fe (x) CrSi (1.3 a parts per thousand currency sign x a parts per thousand currency sign 1.8) . JOURNAL OF THE KOREAN PHYSICAL SOCIETY62 ( 12 ) 2063 - 2067 2013.7Reviewed International journal

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

We have measured the temperature (T) dependences of the electric resistivity, rho(T), and the specific heat, C (p) (T), of the ferromagnetic full-Heusler compound Ru2-x Fe (x) CrSi (1.3 a parts per thousand currency sign x a parts per thousand currency sign 1.8). rho(T) shows a metallic behavior (a,rho/a,T > 0) for 20 a parts per thousand(2) T a parts per thousand currency sign 300 K and nominal upturn at around 20 K for all samples. In the low-temperature range, C (p) (T) can be described by Debye's T (3) law. Although the coefficient of the lattice part of C (p) (T), beta, is insensitive for the Fe concentration x, the electronic specific heat part, gamma, decreases with increasing x. The values of the total densities of states (D (total) (E (F) )) estimated from gamma were 12.8, 10.1, and 9.6 states/f.u. eV for x = 1.3, 1.6, and 1.8, respectively. The values of majority spin band (D (a dagger)(E (F) )) and the minority spin band (D (a dagger")(E (F) )) were also estimated using gamma and the spin polarization P defined by Andreev-reflection experiments.

DOI： 10.3938/jkps.62.2063

Masahiko Hiroi, Kaori Uchida, Iduru Shigeta, Masakazu Ito, Keiichi Koyama, Shojiro Kimura, Kazuo Watanabe . Antiferromagnetic Transition in Ru₂CrSi in Magnetic Fields . Journal of the Korean Physical Society62 2068 - 2072 2013.6Antiferromagnetic Transition in Ru₂CrSi in Magnetic FieldsReviewed

Masakazu Ito, Toru Hisamatsu, Tsugumi Rokkaku, Osamu Murayama, Iduru Shigeta, Masahiko Hiroi . Thermodynamic and transport properties of Ru_2-xFe_xCrSi (1.3 ≦ x ≦ 1.8) . Journal of the Korean Physical Society62 2063 - 2067 2013.6Thermodynamic and transport properties of Ru_2-xFe_xCrSi (1.3 ≦ x ≦ 1.8)Reviewed

Iduru Shigeta, Yuya Sakuraba, Shojiro Kimura, Keiichi Koyama, Kazuo Watanabe, Koki Takanashi, Masahiko Hiroi . Transport and magnetic properties of fully epitaxial superconducting NbN/half-metallic Heulser alloy Co₂MnSi bilayer flms . Journal of the Magnetics Society of Japan37 222 - 226 2013.5Transport and magnetic properties of fully epitaxial superconducting NbN/half-metallic Heulser alloy Co₂MnSi bilayer flmsReviewed

Transport and magnetic properties of fully epitaxial superconducting NbN/half-metallic Heulser alloy Co<sub>2</sub>MnSi bilayer flms . 37 222 - 226 2013.3Transport and magnetic properties of fully epitaxial superconducting NbN/half-metallic Heulser alloy Co<sub>2</sub>MnSi bilayer flmsReviewed International journal

Qing Tao Meng, Shingo Komaki, Takuya Tsuneoka, Hirotoshi Hanada, Shohei Maeda, Taiki Murano, Fusao Ichikawa, Kikuo Itoh, Yuya Nishisako, Iduru Shigeta, Masahiko Hiroi . Tunneling Spectroscopy of the Superconductor-Insulator Transition on Bi2Sr2Ca1-xYxCu2O8+delta and (Bi1-yPby)(2)Sr2Ca1-xYxCu2O8+delta . 2013 IEEE International Conference on Applied Superconductivity and Electromagnetic Devices (ASEMD) 57 - 58 2013Reviewed International journal

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

The purpose of our present study is to understand the Superconductor-Insulator Transition. In this paper we report tunnel experiments on Bi2Sr2Ca1-xYxCu2O8+delta (Y-Bi2212) crystals with x = 0, 0.01, 0.05, 0.1, 0.11 and 0.12. The results are discussed about Copper pairs existing. Tunneling spectra were measured for Y -Bi2212 crystal-SiO-Ag planar junctions. For superconducting samples the V-shape gap structure and zero bias conductance peaks (ZBCP) were observed. While neither superconducting gap nor ZBCP was observed for insulating samples. These results suggest that Cooper pairs break up on the insulating side of SIT. In our spectra there were also several characteristic behaviors.

DOI： 10.1109/ASEMD.2013.6780707

Iduru Shigeta, Yukio Tanaka, Alexander A. Golubov, Masahiko Hiroi . Spin polarized conductance in ferromagnet / insulator / conventional superconductor junctions . Journal of Physics: Conference Series400 032083(1) - -4 2012.12Spin polarized conductance in ferromagnet / insulator / conventional superconductor junctionsReviewed

Iduru Shigeta, Shinpei Urakawa, Masakazu Ito, Masahiko Hiroi . Magnetization and spin polarization of Co_2-xFe_xMnSi Heusler alloys . Journal of Physics: Conference Series400 032082(1) - -5 2012.12Magnetization and spin polarization of Co_2-xFe_xMnSi Heusler alloysReviewed

Masahiko Hiroi, Iori Yano, Kenta Sezaki, Iduru Shigeta, Masakazu Ito, Hirotaka Manaka, Norio Terada . Substitution effect on the magnetic transitions of Fe₂MnSi . Journal of Physics: Conference Series400 032021(1) - -4 2012.12Substitution effect on the magnetic transitions of Fe₂MnSiReviewed

Masahiko Hiroi, Haku Ko, Shingo Nakashima, Iduru Shigeta, Masakazu Ito, Hirotaka Manaka, Norio Terada . Spin-glass and antiferromagnetic transition in Ru_2-xFe_xCrSi . Journal of Physics: Conference Series400 032020(1) - -4 2012.12Spin-glass and antiferromagnetic transition in Ru_2-xFe_xCrSiReviewed

廣井政彦，小山佳一，伊藤昌和，重田出 . ヘリウム液化装置 . 鹿児島大学理学部紀要44 27 - 32 2011.12ヘリウム液化装置

Iduru Shigeta, Osamu Murayama, Toru Hisamatsu, Alexander Brinkman, Alexander A. Golubov, Yukio Tanaka, Masakazu Ito, Hans Hilgenkamp, Masahiko Hiroi . Spin polarization of Fe-rich ferromagnetic compounds in Ru_2-xFe_xCrSi Heusler alloys . Journal of Physics and Chemistry of Solids72 604 - 607 2011.5Spin polarization of Fe-rich ferromagnetic compounds in Ru_2-xFe_xCrSi Heusler alloysReviewed

Iduru Shigeta, Osamu Murayama, Toru Hisamatsu, Alexander Brinkman, Alexander A. Golubov, Yukio Tanaka, Masakazu Ito, Hans Hilgenkamp, Masahiko Hiroi . Spin polarization of Fe-rich ferromagnetic compounds in Ru2-xFexCrSi Heusler alloys . JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS72 ( 5 ) 604 - 607 2011.5Reviewed International coauthorship International journal

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

We report spin polarization P of Ru2-xFexCrSi Heusler alloys by the Andreev reflection technique. Ru2-xFexCrSi with L2(1)-type structure and saturation magnetic moment of 2 mu(B) per formula unit is theoretically predicted to be half-metals in the wide range of the composition x. We had clarified that the experimental results of saturation magnetic moment in Fe-rich compounds had coincided with the theoretical prediction. Therefore, we have measured the differential conductance of Ru2-xFexCrSi/Pb planar-type junctions. The P value of Ru2-xFexCrSi was determined by fitting the differential conductance with the modified Blonder-Tinkham-Klapwijk theory. We have found that the behavior of P for Ru2-xFexCrSi was independent of the composition x in the Fe-rich region: P=0.53 for both of x=1.5 and 1.7. The spin polarization is the similar value to Co-based Heusler alloys. (C) 2010 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jpcs.2010.10.062

Masakazu Ito, Toru Hisamatsu, Shingo Nakashima, Iduru Shigeta, Kazuyuki Matsubayashi, Yoshiya Uwatoko, Masahiko Hiroi . Transport properties of Heusler compound Ru_2-xFe_xCrSi under pressure . Journal of Physics: Conference Series266 012011(1) - -4 2011.1Transport properties of Heusler compound Ru_2-xFe_xCrSi under pressureReviewed

Masahiko Hiroi, Shingo Nakashima, Kouhei Nakao, Tsugumi Rokkaku, Masakazu Ito, Iduru Shigeta, Hirotaka Manaka, Norio Terada . Magnetic properties of Ru-rich Ru_2-xFe_xCrZ (Z = Si, Ge) . Journal of Superconductivity and Novel Magnetism24 753 - 756 2011.1Magnetic properties of Ru-rich Ru_2-xFe_xCrZ (Z = Si, Ge)Reviewed

Masahiko Hiroi, Shingo Nakashima, Kohei Nakao, Tsugumi Rokkaku, Masakazu Ito, Iduru Shigeta, Hirotaka Manaka, Norio Terada . Magnetic Properties of Ru-rich Ru(2-x)Fe(x)CrZ (Z=Si, Ge) . JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM24 ( 1-2 ) 753 - 756 2011.1Reviewed International journal

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

The properties of Heusler compounds Ru2-x Fe (x) CrGe are investigated and compared with those of Ru1.9Fe0.1CrSi. Ru2CrGe is confirmed to exhibit an antiferromagnetic transition with Ne,l temperature 13 K by magnetic susceptibility and specific heat measurements. When Fe is substituted for Ru, a peak in the magnetic susceptibility is observed, and in the lower temperature region irreversibility between temperature dependences of magnetization for zero-field-cooling and field-cooling conditions is found. Nevertheless, in specific heat of Ru1.9Fe0.1CrGe, there is no anomaly to indicate phase transition. The specific heat is almost identical to that for Ru1.9Fe0.1CrSi. The above results demonstrate that the magnetic states in the low temperature region of Fe-substituted samples are spin-glass-like states. Slight substitution of Fe for Ru destroys the long-range-order and lead to peculiar spin-glass-like states.

DOI： 10.1007/s10948-010-0967-6

Masakazu Ito, Toru Hisamatsu, Shingo Nakashima, Iduru Shigeta, Kazuyosi Matsubayashi, Yoshiya Uwatoko, Masahiko Hiroi . Transport Properties of Heusler Compound Ru2-xFexCrSi under Pressure . 2ND INTERNATIONAL SYMPOSIUM ON ADVANCED MAGNETIC MATERIALS AND APPLICATIONS (ISAMMA 2010)266 012011-1 - 012011-4 2011Reviewed International journal

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

We investigated transport properties of the full-Heusler compound Ru2-xFexCrSi (x = 0.1), which is an insulator, under pressure P up to 8 GPa. The temperature dependence of electric resistance R(T) for Ru1.9Fe0.1CrSi is insensitive to pressure. R(T) is not described by the simple activation-type but -logT in the wide T and all P range we measured. This might be due to atomic disorder in the crystalline.

DOI： 10.1088/1742-6596/266/1/012011