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Journal Articles

Doping-dependent Fe phonon dynamics in LaFeAsO$$_{1-x}$$H$$_x$$ studied by $$^{57}$$Fe nuclear resonant inelastic scattering

Kawachi, Shiro*; Hiraka, Haruhiro*; Yamaura, Junichi*; Iimura, Soshi*; Nakamura, Hiroki; Tsutsui, Satoshi*; Yoda, Yoshitaka*; Machida, Masahiko; Hosono, Hideo*; Kobayashi, Hisao*

Physical Review B, 113(2), p.024519_1 - 024519_7, 2026/01

https://doi.org/10.1103/7zd9-5t9z
 Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)

To investigate the phonon dynamics of iron in the heavily hydride-ion-substituted region of LaFeAsO$$_{1-x}$$H$$_x$$ ($$x > 0.2$$), $$^{57}$$Fe nuclear resonant inelastic scattering measurements were performed over a wide temperature range from 5 to 300 K on two polycrystalline samples with $$x = 0.35$$ and 0.51, which exhibit superconducting and antiferromagnetic ground states, respectively. The resulting inelastic scattering spectra revealed distinct differences between the two compositions. The Fe phonon density of states (PDOS) exhibits a pronounced peak at 15 meV for $$x = 0.35$$, whereas this peak is absent in $$x = 0.51$$. Density functional theory calculations support the interpretation that the PDOS peak at 15 meV is associated with the optical vibrational modes of Fe atoms along the nearest-neighbor direction, mediated by As atoms. The calculations further suggest that the suppression of the PDOS peak at 15 meV for $$x = 0.51$$ originates from in-plane electronic inequivalence. These findings suggest that signatures of electronic nematicity may persist over a wide temperature range in the $$x = 0.51$$ composition, which exhibits magnetic and structural order, whereas such signatures are almost absent in the superconducting $$x = 0.35$$ composition.

Journal Articles

Quasielastic neutron scattering probing H$$^{-}$$ dynamics in the H$$^{-}$$ conductors LaH$$_{3-2x}$$O$$_{x}$$

Tamatsukuri, Hiromu; Fukui, Keiga*; Iimura, Soshi*; Honda, Takashi*; Tada, Tomofumi*; Murakami, Yoichi*; Yamaura, Junichi*; Kuramoto, Yoshio*; Sagayama, Hajime*; Yamada, Takeshi*; et al.

Physical Review B, 107(18), p.184114_1 - 184114_8, 2023/05

https://doi.org/10.1103/PhysRevB.107.184114
 Times Cited Count：2 Percentile：13.49(Materials Science, Multidisciplinary)

Journal Articles

Quantum dynamics of hydrogen in the iron-based superconductor LaFeAsO$$_{0.9}$$D$$_{0.1}$$ measured with inelastic neutron spectroscopy

Yamaura, Junichi*; Hiraka, Haruhiro*; Iimura, Soshi*; Muraba, Yoshinori*; Bang, J.*; Ikeuchi, Kazuhiko*; Nakamura, Mitsutaka; Inamura, Yasuhiro; Honda, Takashi*; Hiraishi, Masatoshi*; et al.

Physical Review B, 99(22), p.220505_1 - 220505_6, 2019/06

AA2019-0126.pdf:0.9MB

https://doi.org/10.1103/PhysRevB.99.220505
 Times Cited Count：4 Percentile：15.88(Materials Science, Multidisciplinary)

Inelastic neutron scattering was performed for an iron-based superconductor, where most of D (deuterium) replaces oxygen, while a tiny amount goes into interstitial sites. By first-principle calculation, we characterize the interstitial sites for D (and for H slightly mixed) with four equivalent potential minima. Below the superconducting transition temperature Tc = 26 K, new excitations emerge in the range 5-15 meV, while they are absent in the reference system LaFeAsO$$_{0.9}$$F$$_{0.1}$$. The strong excitations at 14.5 meV and 11.1 meV broaden rapidly around 15 K and 20 K, respectively, where each energy becomes comparable to twice of the superconducting gap. The strong excitations are ascribed to a quantum rattling, or a band motion of hydrogen, which arises only if the number of potential minima is larger than two.

Journal Articles

Gapless magnetic excitation in a heavily electron-doped antiferromagnetic phase of LaFeAsO$$_{0.5}$$D$$_{0.5}$$

Tamatsukuri, Hiromu*; Hiraka, Haruhiro*; Ikeuchi, Kazuhiko*; Iimura, Soshi*; Muraba, Yoshinori*; Nakamura, Mitsutaka; Sagayama, Hajime*; Yamaura, Junichi*; Murakami, Yoichi*; Kuramoto, Yoshio*; et al.

Physical Review B, 98(17), p.174415_1 - 174415_6, 2018/11

AA2018-0436.pdf:0.85MB

https://doi.org/10.1103/PhysRevB.98.174415
 Times Cited Count：4 Percentile：16.30(Materials Science, Multidisciplinary)

Magnetic excitations in a heavily electron-doped antiferromagnet, LaFeAsO$$_{0.5}$$D$$_{0.5}$$, have been investigated using powder inelastic neutron scattering. Unlike other parent compounds of the iron-based superconductors, the magnetic excitation gap in LaFeAsO$$_{0.5}$$D$$_{0.5}$$ was not detected down to the lowest measured temperature of 4 K. This result can be understood as a result of quasi-isotropy within the ab plane, which is consistent with the band calculation result that the $$d_{xy}$$ orbital plays the dominant role in the magnetism of LaFeAsO$$_{0.5}$$H$$_{0.5}$$. In addition, the intensities of the magnetic excitations in this phase are much stronger than those in nondoped LaFeAsO. Even in the paramagnetic phase, the magnetic excitation in LaFeAsO$$_{0.5}$$D$$_{0.5}$$ persists. These results corroborate recent studies showing that the electron doping enhances the localized nature in this system.

Journal Articles

Bipartite magnetic parent phases in the iron oxypnictide superconductor

Hiraishi, Masatoshi*; Iimura, Soshi*; Kojima, Kenji*; Yamaura, Junichi*; Hiraka, Haruhiro*; Ikeda, Kazutaka*; Miao, P.*; Ishikawa, Yoshihisa*; Torii, Shuki*; Miyazaki, Masanori*; et al.

Nature Physics, 10(4), p.300 - 303, 2014/04

https://doi.org/10.1038/nphys2906
 Times Cited Count：115 Percentile：94.88(Physics, Multidisciplinary)

Journal Articles

Orbital magnetism in Cd$$_2$$Os$$_2$$O$$_7$$ studied by X-ray magnetic circular dichroism

Matsuda, Yasuhiro*; Her, J.-L.*; Michimura, Shinji*; Inami, Toshiya; Suzuki, Motohiro*; Kawamura, Naomi*; Mizumaki, Masaichiro*; Kindo, Koichi*; Yamaura, Junichi*; Hiroi, Zenji*

Physical Review B, 84(17), p.174431_1 - 174431_5, 2011/11

https://doi.org/10.1103/PhysRevB.84.174431
 Times Cited Count：27 Percentile：69.18(Materials Science, Multidisciplinary)

X-ray magnetic circular dichroism (XMCD) at the $$L$$$$_{2,3}$$-edge of Os has been investigated in the antiferromagneticphase of Cd$$_2$$Os$$_2$$O$$_7$$, which exhibits a metal-insulator transition around 227 K. According to the sum rule, the XMCD spectra at 10 and 37 T clearly show that the ratio between the orbital magnetic moment ($$m_{rm L}$$) and spinmagnetic moment ($$m_{rm S}$$) is $$m_{rm L}/m_{rm S} = 0.16 pm 0.02$$, and that $$m_{rm L}$$ and $$m_{rm S}$$ are coupled in parallel ($$m_{rm L}parallel m_{rm S}$$). These phenomena are unusual in that the expected ground state of Os$$^{5+}$$ (5$$d^3$$) is an orbital singlet in a cubic crystal field, and $$m_{rm L}$$and $$m_{rm S}$$ should be antiparallel for a less than half-filled system in accordance with Hund's third rule. It is likely that the spin-orbit coupling is important for explaining the observed orbital magnetism.

Journal Articles

Electrical and magnetic properties of a single crystal UCu$$_2$$Si$$_2$$

Matsuda, Tatsuma; Haga, Yoshinori; Ikeda, Shugo; Galatanu, A.; Yamamoto, Etsuji; Shishido, Hiroaki*; Yamada, Mineko*; Yamaura, Junichi*; Hedo, Masato*; Uwatoko, Yoshiya*; et al.

Journal of the Physical Society of Japan, 74(5), p.1552 - 1556, 2005/05

https://doi.org/10.1143/JPSJ.74.1552
 Times Cited Count：26 Percentile：72.53(Physics, Multidisciplinary)

We have succeeded in growing a high-quality single crystal of UCu$$_2$$Si$$_2$$ with the tetragonal structure by the Sn-flux method and measured the electrical resistivity, magnetic susceptibility, magnetization and specific heat. UCu$$_2$$Si$$_2$$ is found to order antiferromagnetically below $$T_{rm N}$$ = 106 K, and follows a successive ferromagnetic ordering at $$T_{rm C}$$ = 100 K. The magnetic properties are highly anisotropic, reflecting the crystal structure. An easy-axis of magnetization is found to be the [001] direction ($$c$$-axis) both in the antiferromagnetic and ferromagnetic phases, while the [100] direction ($$a$$-axis) corresponds to the hard-axis in magnetization. The magnetization curve in the antiferromagnetic phase indicates a clear metamagnetic transition at a low field of about 1 kOe and changes smoothly into a ferromagnetic magnetization curve below $$T_{rm C}$$ = 100 K. The saturation moment is determined as 1.75$$mu_{rm B}$$/U at 2 K. The electronic specific heat coefficient is also determined as 20 mJ/K$$^2$$$$cdot$$mol.

Journal Articles

Electrical properties of neutron-irradiated oxygen potential sensors using stabilized zirconia solid electrolyte

; Endo, Yasuichi; Yamaura, Takayuki; Hoshiya, Taiji; Niimi, Motoji; Saito, Junichi; ; Ooka, Norikazu; Kobiyama, M.*

Journal of Nuclear Materials, 258-263, p.2041 - 2045, 1998/00

https://doi.org/10.1016/S0022-3115(98)00125-1
 Times Cited Count：6 Percentile：48.20(Materials Science, Multidisciplinary)

no abstracts in English

JAEA Reports

Neutron irradiation characteristic tests of oxygen sensors using zirconia solid electrolyte

; Endo, Yasuichi; Yamaura, Takayuki; Niimi, Motoji; Hoshiya, Taiji; Saito, Junichi; ; Ooka, Norikazu;

JAERI-Research 97-028, 46 Pages, 1997/03

JAERI-Research-97-028.pdf:2.49MB

no abstracts in English

Oral presentation

Quasielastic neutron scattering probing H$$^{-}$$ dynamics in the H$$^{-}$$ conductors LaH$$_{3-2x}$$O$$_{x}$$

Tamatsukuri, Hiromu; Fukui, Keiga*; Iimura, Soshi*; Honda, Takashi*; Tada, Tomofumi*; Murakami, Yoichi*; Yamaura, Junichi*; Kuramoto, Yoshio*; Sagayama, Hajime*; Yamada, Takeshi*; et al.

no journal, , 

no abstracts in English

Oral presentation

Quasielastic neutron scattering probing H$$^{-}$$ dynamics in the H$$^{-}$$ conductors LaH$$_{3-2x}$$O$$_{x}$$

Tamatsukuri, Hiromu; Fukui, Keiga*; Iimura, Soshi*; Honda, Takashi*; Tada, Tomofumi*; Murakami, Yoichi*; Yamaura, Junichi*; Kuramoto, Yoshio*; Sagayama, Hajime*; Yamada, Takeshi*; et al.

no journal, , 

no abstracts in English

Oral presentation

Quasielastic neutron scattering probing H$$^{-}$$ dynamics in the H$$^{-}$$ conductors LaH$$_{3-2x}$$O$$_{x}$$

Tamatsukuri, Hiromu; Fukui, Keiga*; Iimura, Soshi*; Honda, Takashi*; Tada, Tomofumi*; Murakami, Yoichi*; Yamaura, Junichi*; Kuramoto, Yoshio*; Sagayama, Hajime*; Yamada, Takeshi*; et al.

no journal, , 

A series of oxyhydrides LaH$$_{3-2x}$$O$$_{x}$$ exhibits characteristic high H$$^{-}$$ conductivity. In this study, we performed the incoherent quasielastic neutron scattering measurements to investigate H$$^{-}$$ dynamics in LaH$$_{3-2x}$$O$$_{x}$$. We successfully identify two kinds of microscopic H$$^{-}$$ dynamics in the end member LaH$$_{3}$$; the jump diffusion and the localized back and forth jump between neighboring tetrahedral and octahedral sites. These dynamics have the common elementary jump process between the Tet and adjacent Oct sites, and become more conspicuous with increasing a concentration of H$$^{-}$$. Based on these results, we discuss that the origin of the high H$$^{-}$$ conductivity in this system is explained by a so-called concerted migration model.

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