Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Ikeda, Shugo*; Kaneko, Koji; Tanaka, Yuki*; Kawasaki, Takuro; Hanashima, Takayasu*; Munakata, Koji*; Nakao, Akiko*; Kiyanagi, Ryoji; Ohara, Takashi; Mochizuki, Kensei*; et al.
Journal of the Physical Society of Japan, 89(1), p.014707_1 - 014707_7, 2020/01
Times Cited Count：1 Percentile：12.02(Physics, Multidisciplinary)
AsIkeda, Shugo*; Tsuchiya, Yu*; Zhang, X.-W.*; Kishimoto, Shunji*; Kikegawa, Takumi*; Yoda, Yoshitaka*; Nakamura, Hiroki; Machida, Masahiko; Glasbrenner, J.*; Kobayashi, Hisao*
Physical Review B, 98(10), p.100502_1 - 100502_6, 2018/09
Times Cited Count：6 Percentile：25.82(Materials Science, Multidisciplinary)The interplay between magnetism and superconductivity is one of important subjects to investigate the pairing mechanism in novel superconductors. We have found new coexistence between an antiferromagnetic order in the Fe sublattice and superconductivity of the FeAs-based EuFeAs superconductor in the pressure range from 2.4 to 3.0 GPa by 
Fe nuclear forward scattering (NFS) using a single crystal sample. The magnetic state in the Fe sublattice changes to a new antiferromagnetic one with superconductivity from a stripe-type antiferromagnetic one observed in normal conducting state at 2.7 GPa. Below the superconducting transition temperature, the temperature dependence of Fe NFS spectra reveals that the new antiferromagnetic order develops with the superconductivity. This non-trivial coupling of two ordered states in EuFeAs under pressure demonstrates a new and intriguing relationship between magnetism and superconductivity in Fe-based superconductors.
Tateiwa, Naoyuki; Haga, Yoshinori; Matsuda, Tatsuma*; Fisk, Z.; Ikeda, Shugo*; Kobayashi, Hisao*
Review of Scientific Instruments, 84(4), p.046105_1 - 046105_3, 2013/04
Times Cited Count：13 Percentile：52.34(Instruments & Instrumentation)Two modifications have been made to a miniature ceramic anvil high pressure cell (mCAC) designed for magnetic measurements in a commercial superconducting quantum interference (SQUID) magnetometer. Replacing the Cu-Be piston in the former mCAC with a composite piston composed of the Cu-Be and ceramic cylinders reduces the background magnetization significantly smaller at low temperatures. A second modification to the mCAC is the utilization of a ceramic anvil with a hollow in the center of the culet surface.
AsKobayashi, Hisao*; Ikeda, Shugo*; Sakaguchi, Yui*; Yoda, Yoshitaka*; Nakamura, Hiroki; Machida, Masahiko
Journal of Physics; Condensed Matter, 25(2), p.022201_1 - 022201_6, 2013/01
Times Cited Count：9 Percentile：40.37(Physics, Condensed Matter)The electronic and vibrational properties of EuFeAs in the tetragonal phase between 0 and 5 GPa have been investigated using Fe M
ssbauer spectroscopy and Fe nuclear resonance inelastic scattering, respectively. We find a discontinuous increase of the center shift around 2.3 GPa, reflecting a change of the electronic state of Fe, and above 2.5 GPa a softening of the optical phonon modes associated with an increase of the relative volume of the FeAs tetrahedron in the unit cell. Our findings reveal that an effective As-As hybridization along the c axis appears at approximately 2.3 GPa in the tetragonal phase of EuFeAs, along with a change in the electronic state of Fe, causing bulk superconductivity to appear at a low temperature. Consequently, the change in the electronic state of the Fe atom and the effective As-As hybridization play key roles in the pressure-induced superconductivity in the tetragonal phase of AFeAs.
Fe2As ( = Sr and Eu)Kobayashi, Hisao*; Ikeda, Shugo*; Yoda, Yoshitaka*; Nakamura, Hiroki; Machida, Masahiko
Physical Review B, 84(18), p.184304_1 - 184304_7, 2011/11
Times Cited Count：9 Percentile：39.35(Materials Science, Multidisciplinary)The structural and magnetic phase transition in FeAs ( = Sr and Eu) was investigated from the viewpoint of the Fe-specific phonon density of states, 
(
), utilizing Fe nuclear resonant inelastic-scattering and ab initio phonon calculations. The Fe optical phonon branches in () around 25 meV show no anomalies across the phase transition temperature, 
, with decreasing temperature. Meanwhile, the peak intensity around 32 meV decreases and increases at 1.25 and , respectively, which originates from phonon branches involving Fe and As atomic displacements in the tetragonal structure. This decrease is related to the phonon branches involving atomic displacements in the ab plane. Furthermore, the average sound velocity below 8 meV shows no temperature dependence down to , suggesting softening in some of the sound waves. Our results indicate the presence of orthorhombic fluctuations in tetragonal FeAs.
Sato, Nobuyuki; ; Kobayashi, Makoto; Nakazawa, Takashi; ; ; Ikezawa, Yoshio
Proc. of the Int. Conf. on Radiation Effects and Protection, p.440 - 445, 1992/00
no abstracts in English
AsFukuda, Tatsuo; Kobayashi, Hisao*; Ikeda, Shugo*; Tsuchiya, Yu*; Tsutsui, Satoshi*; Baron, A. Q. R.*; Nakamura, Hiroki; Machida, Masahiko
no journal, ,
no abstracts in English
=7/2 family Eu
In (=Ni, Pd, Pt)Kaneko, Koji; Ikeda, Shugo*; Frontzek, M. D.*; Hanashima, Takayasu*; Nakao, Akiko*; Kiyanagi, Ryoji; Ohara, Takashi; Homma, Yoshiya*; Kobayashi, Hisao*; Yamagami, Hiroshi
no journal, ,
InKaneko, Koji; Ikeda, Shugo*; Frontzek, M. D.*; Cao, H.*; Hanashima, Takayasu*; Nakao, Akiko*; Kiyanagi, Ryoji; Ohara, Takashi; Kobayashi, Hisao*; Yamagami, Hiroshi
no journal, ,
no abstracts in English
