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Tokunaga, Yo; Aoki, Dai*; Mayaffre, H.*; Kr
mer, S.*; Julien, M.-H.*; Berthier, C.*; Horvati
, M.*; Sakai, Hironori; Kambe, Shinsaku; Hattori, Taisuke; et al.
JPS Conference Proceedings (Internet), 30, p.011037_1 - 011037_6, 2020/03
The field-angular dependence of Co-NMR spin-lattice relaxation rate 
has been measured for a 10% Co-doped single crystal of URhGe. The experiment revealed that spin fluctuations in ferromagnetic (FM) state of URhGe are robust against magnetic field below about 4 T, applied along any direction in the 
crystal plane. This is in clear contrast with the sister compound UCoGe, in which FM spin fluctuations are rapidly suppressed by a tiny applied field along the 
axis. We show that such a difference in the character of the spin fluctuations is reflected in their two distinct phase diagrams for the upper critical field 
, providing further support to the mechanism of superconductivity mediated by spin fluctuations in these materials.
Te-NMR study on a single crystal of heavy fermion superconductor UTe
Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Hattori, Taisuke; Higa, Nonoka; Nakamine, Genki*; Kitagawa, Shunsaku*; Ishida, Kenji*; Nakamura, Ai*; Shimizu, Yusei*; et al.
Journal of the Physical Society of Japan, 88(7), p.073701_1 - 073701_4, 2019/07
Times Cited Count：59 Percentile：94.56(Physics, Multidisciplinary)We report Te-NMR studies on a newly discovered heavy fermion superconductor UTe. Using a single crystal, we have measured the Te-NMR Knight shift 
and spin-lattice relaxation rate for fields along the three orthorhombic crystal axes. The data confirm a moderate Ising anisotropy for both the static () and dynamical susceptibilities () in the paramagnetic state above about 20 K. Around 20 K, however, we have observed a sudden loss of NMR spin-echo signal due to sudden enhancement of the NMR spin-spin relaxation rate 
, when the field is applied along the easy axis of magnetization (=
axis). This behavior suggests the development of longitudinal magnetic fluctuations along the axis at very low frequencies below 20 K.
iron-based superconductor LaFePO
Ishikado, Motoyuki*; Shamoto, Shinichi; Kodama, Katsuaki; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Hong, T.*; Mutka, H.*
Scientific Reports (Internet), 8, p.16343_1 - 16343_6, 2018/11
Times Cited Count：3 Percentile：29(Multidisciplinary Sciences)Spin fluctuations are widely believed to play an important role as one of the most possible mechanisms for unconventional high-temperature superconductors. Here, the spin fluctuation in LaFePO is found at high energies such as 30-50 meV with comparable intensity to an optimally doped LaFeAs(O,F).
-electron systems with filled skutterudite structureHotta, Takashi
Journal of the Physical Society of Japan, 74(4), p.1275 - 1288, 2005/04
Times Cited Count：25 Percentile：72.87(Physics, Multidisciplinary)In order to understand electronic properties of filled skutterudite materials, the Anderson model is analyzed by using the numerical renormalization group method to evaluate magnetic susceptibility and entropy of electron for each case of 
=1
13, where is the number of electrons per rare-earth ion. For the 
-electron system corresponding to the Pr-based filled skutterudite, it is found that magnetic fluctuations significantly remain at low temperatures, even when the ground state is 
singlet, if 
triplet is the excited state with small excitation energy. By analyzing an orbital degenerate Hubbard model constructed based on the 
- coupling scheme, we find that anisotropic Cooper-pair mediated by magnetic fluctuations appears in a limited region in which the singlet and triplet ground states are interchanged.
-electron systemsHotta, Takashi
Physica B; Condensed Matter, 359-361, p.1003 - 1005, 2005/04
Times Cited Count：1 Percentile：6.21(Physics, Condensed Matter)In order to understand magnetic properties of filled skutterudite materials, we evaluate magnetic susceptibility of the Anderson model with orbital degeneracy by using the numerical renormalization group method. Even when the local ground state is , magnetic fluctuations significantly remain, if is the excited state with small excitation energy, as experimentally proposed for Pr-based filled skutterudite compounds.
Hotta, Takashi
Physical Review Letters, 94(6), p.067003_1 - 067003_4, 2005/02
Times Cited Count：15 Percentile：62.67(Physics, Multidisciplinary)In order to clarify magnetic properties of filled skutterudites, we analyze the Anderson model including seven orbitals hybridized with an 
conduction band using a numerical technique. For =2 corresponding to Pr-based filled skutterudites, where is the local -electron number, even if the ground state is a singlet, there remain significant magnetic fluctuations from a triplet state with a small excitation energy. This result can be understood by the fact that -electron states are clearly distinguished as itinerant and localized ones in the filled skutterudite structure. This picture also explains the complex results for -electron magnetic susceptibility and entropy for =113.
Koizumi, Satoshi; Monkenbusch, M.*; Richter, D.*; Schwahn, D.*; Farago, B.*
Journal of Chemical Physics, 121(24), p.12721 - 12731, 2004/12
Times Cited Count：57 Percentile：85.88(Chemistry, Physical)no abstracts in English
Takemoto, Hiroki*; Fukushima, Masahiro; Chiba, Satoshi; Horiuchi, Hisashi*; Akaishi, Yoshinori*; Tosaki, Akihiro*
Physical Review C, 69(3), p.035802_1 - 035802_9, 2004/03
Times Cited Count：30 Percentile：81.64(Physics, Nuclear)no abstracts in English
Machida, Masahiko; Itakura, Mitsuhiro
Physica C, 392-396(1-4), p.331 - 335, 2003/10
no abstracts in English
Koizumi, Satoshi
Kobunshi, 51(12), P. 957, 2002/12
no abstracts in English
Ga
Abe, Hideki*; Yoshii, Kenji; Kitazawa, Hideaki*
Journal of the Physical Society of Japan, 70(10), p.3042 - 3045, 2001/10
Times Cited Count：9 Percentile：51.41(Physics, Multidisciplinary)no abstracts in English
Onuma, Masato*; Suzuki, Junichi; Funahashi, Satoru; *; Kuwano, Hisashi*; *
Mater. Trans. JIM, 36(7), p.918 - 923, 1995/07
Times Cited Count：7 Percentile：52.43(Materials Science, Multidisciplinary)no abstracts in English
Onuma, Masato*; Suzuki, Junichi; Funahashi, Satoru; *; Kuwano, Hisashi*; *
Physica B; Condensed Matter, 213-214, p.582 - 584, 1995/00
Times Cited Count：7 Percentile：45.18(Physics, Condensed Matter)no abstracts in English
Matsubara, Akihiro; Fujita, Natsuko; Nishizawa, Akimitsu*; Miyake, Masayasu*
no journal, ,
no abstracts in English
CTamatsukuri, Hiromu; Murakami, Yoichi*; Kuramoto, Yoshio*; Sagayama, Hajime*; Matsuura, Masato*; Kawakita, Yukinobu; Matsuishi, Satoru*; Washio, Yasuhito*; Inoshita, Takeshi*; Hamada, Noriaki*; et al.
no journal, ,
no abstracts in English
Tokunaga, Yo; Sakai, Hironori; Kambe, Shinsaku; Opletal, P.; Tokiwa, Yoshifumi; Haga, Yoshinori
no journal, ,
no abstracts in English
K
FeAs as seen via time-of-flight neutron spectroscopyKajimoto, Ryoichi; Kofu, Maiko; Kawamura, Seiko; Suzuki, Katsuhiro*; Nakajima, Masamichi*; Murai, Naoki
no journal, ,
The spin dynamics of iron-based superconductors is believed to play an essential role in the pairing mechanism, but realistic modeling of magnetic neutron scattering spectra in these materials remains challenging owing to their complex multi-band structure. Here we report the results of inelastic neutron scattering measurements of BaKFeAs that provide a benchmark of an ab-initio approach of the dynamical spin susceptibility. Our main results are two-fold. First, the magnetic neutron scattering response exhibits periodic intensity modulation along the out-of-plane direction. The observed periodicity corresponds to the out-of-plane warping of Fermi surfaces, revealing the importance of nesting in three-dimensional momentum space. Second, our careful measurements reveal the existence of the theoretically predicted multiple resonant modes that result from the multiple superconducting gaps. The agreement between theory and experiment in the present work highlights the potential of neutron spectroscopy to investigate the complex multi-band structure of iron-based superconductors.
