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Tokiwa, Yoshifumi; Sakai, Hironori; Kambe, Shinsaku; Opletal, P.; Yamamoto, Etsuji; Kimata, Motoi*; Awaji, Satoshi*; Sasaki, Takahiko*; Yanase, Yoichi*; Haga, Yoshinori; et al.
Physical Review B, 108(14), p.144502_1 - 144502_5, 2023/10
Times Cited Count：0 Percentile：0(Materials Science, Multidisciplinary)The vortex dynamics in the spin-triplet superconductor, UTe, are studied by measuring the DC electrical resistivity with currents along the 
-axis under magnetic fields along the 
-axis. Surprisingly, we have discovered an island region of low critical current deep inside the superconducting (SC) state, well below the SC upper critical field, attributed to a weakening of vortex pinning. Notably, this region coincides with the recently proposed intermediate-field SC state. We discuss the possibility of nonsingular vortices in the intermediate state, where SC order parameter does not vanish entirely in the vortex cores due to the mixing of multiple SC components.
Te
Opletal, P.; Sakai, Hironori; Haga, Yoshinori; Tokiwa, Yoshifumi; Yamamoto, Etsuji; Kambe, Shinsaku; Tokunaga, Yo
Journal of the Physical Society of Japan, 92(3), p.034704_1 - 034704_5, 2023/03
Times Cited Count：1 Percentile：52.21(Physics, Multidisciplinary)We investigate the physical properties of a single crystal of uranium telluride UTe. We have confirmed that UTe crystallizes in the hexagonal structure with three nonequivalent crystallographic uranium sites. The paramagnetic moments are estimated to be approximately 1 
per the uranium site, assuming a uniform moment on all the sites. A ferromagnetic phase transition occurs at 
= 48 K, where the in-plane magnetization increases sharply, whereas the out of-plane component does not increase significantly. With decreasing temperature further below under field-cooling conditions, the out-of-plane component increases rapidly around T
= 26 K. In contrast, the in-plane component hardly changes at T. Specific heat measurement indicates no 
-type anomaly around T, so this is a cross-over suggesting a reorientation of the ordering moments or successive magnetic ordering on the part of the multiple uranium sites.
by molten salt flux methodSakai, Hironori; Opletal, P.; Tokiwa, Yoshifumi; Yamamoto, Etsuji; Tokunaga, Yo; Kambe, Shinsaku; Haga, Yoshinori
Physical Review Materials (Internet), 6(7), p.073401_1 - 073401_10, 2022/07
Times Cited Count：18 Percentile：90.63(Materials Science, Multidisciplinary)The molten salt flux method is applied as a new synthetic route for the single crystals of the spin-triplet superconductor UTe. The single crystals under an optimized growth condition with excess uranium exhibit a superconducting transition at 
K, which is the highest 
reported for this compound. The obtained crystals show a remarkably large residual resistivity ratio with respect to the room temperature value and a small residual electronic contribution in specific heat well below . These results indicate that the increase of in UTe can be achieved by reducing the disorder associated with uranium vacancies. The excess uranium in the molten salt acts as a reducing agent, preventing tetravalent uranium from becoming pentavalent and suppressing creation of uranium vacancies. At the same time, the relatively low growth temperature can suppress Te volatilization.
Haga, Yoshinori; Opletal, P.; Tokiwa, Yoshifumi; Yamamoto, Etsuji; Tokunaga, Yo; Kambe, Shinsaku; Sakai, Hironori
Journal of Physics; Condensed Matter, 34(17), p.175601_1 - 175601_7, 2022/04
Times Cited Count：18 Percentile：89.04(Physics, Condensed Matter)Fujimori, Shinichi; Okochi, Takuo*; Kawasaki, Ikuto; Yasui, Akira; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Yamagami, Hiroshi; Haga, Yoshinori; et al.
Journal of the Physical Society of Japan, 81(1), p.014703_1 - 014703_9, 2012/01
Times Cited Count：37 Percentile：81.99(Physics, Multidisciplinary)High-energy-resolution core-level and valence-band photoelectron spectroscopic studies were performed for the heavy Fermion uranium compounds UGe, UCoGe, URhGe, URuSi, UNiAl
, UPdAl, and UPt as well as typical localized and itinerant uranium compounds to understand the relationship between the uranium valence state and their core-level spectral line shapes. The core-level spectra of UGe, UCoGe, URhGe, URuSi, and UNiAl are rather similar to those of itinerant compounds, suggesting that U 5
electrons in these compounds are well hybridized with ligand states. On the other hand, the core-level spectra of UPdAl and UPt show considerably different spectral line shapes from those of the itinerant compounds, suggesting that U 5 electrons in UPdAl and UPt are less hybridized with ligand states, leading to the correlated nature of U 5 electrons in these compounds.
Hasegawa, Noboru; Ochi, Yoshihiro; Kawachi, Tetsuya; Nishikino, Masaharu; Ishino, Masahiko; Imazono, Takashi; Kaihori, Takeshi; Sasaki, Akira; Terakawa, Kota*; Minami, Yasuo*; et al.
Proceedings of SPIE, Vol.8140, p.81400G_1 - 81400G_8, 2011/10
Times Cited Count：3 Percentile：82.06(Engineering, Electrical & Electronic)We have developed a soft X-ray laser (SXRL) interferometer capable of the single-shot imaging of nano-scaled structure dynamics. The interferometer consisted of the reflection optics including double Lloyd's mirrors and focusing optics, and the interference fringes are produced on the detector surface. By using this interferometer, the initial stage (
50 ps) of the ablation process of the Pt surface pumped by a 70 fs Ti:Sapphire laser pulse was observed. The expansion speed of the surface estimated from the result (34 nm/50 ps) indicated that the nano-bubble structures were formed in the initial stage of the ablation. In order to observe the detailed dynamics, the temporal synchronization between the pump and probe pulses was improved to be 3 ps by adopting a portion of the SXRL and pump beams as the time fiducials, to which the pump and probe timing was adjusted by using the X-ray streak camera.
Yamamoto, Minoru; Hasegawa, Noboru; Terakawa, Kota*; Umeda, Yoshifumi*; Tomita, Takuro*; Ochi, Yoshihiro; Nishikino, Masaharu; Ishino, Masahiko; Imazono, Takashi; Kaihori, Takeshi; et al.
Proceedings of 12th International Symposium on Laser Precision Microfabrication (LPM 2011) (Internet), 4 Pages, 2011/06
Femtosecond lasers have been used for material processing. However, the physical processes responsible for femtosecond laser ablation have not been understood completely. These processes involve melting, vaporization, re-solidification or ablation, which occur in a very short time from pico- to nano-seconds. To understand the physical processes, it is essential to reveal the dynamics of ultrafast surface morphological change after laser irradiation. At JAEA, the laser-driven plasma soft X-ray laser (SXRL) that has extremely high spatial and spectral purity was constructed. It delivers soft X-ray photons at 89.2 eV (13.9 nm) with a photon number of exceeding 
, which is sufficient to obtain a single shot interferogram. By using this system, the soft X-ray laser interferometer with the lateral resolution of 1.8 
m and a depth resolution of 1 nm was developed. We report on demonstration of time-resolved measurement of femtosecond-laser ablation dynamics by using the soft X-ray laser interferometer.
Fujimori, Shinichi; Terai, Kota; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Muramatsu, Yasuji; Fujimori, Atsushi; Yamagami, Hiroshi*; Ikeda, Shugo; Matsuda, Tatsuma; et al.
Physica B; Condensed Matter, 378-380, p.995 - 996, 2006/05
Times Cited Count：2 Percentile：12.53(Physics, Condensed Matter)Recently, photoemission experiments in soft X-ray region have attracted much attention due to their high sensitivities for bulk electronic structures of strongly correlated electron system. We have carried out the high-resolution photoemission experiments on some uranium compounds using soft X-ray synchrotron radiation from SPring-8 to understand their electronic structures. Bulk- and U 5-sensitive band structure and Fermi surface were obtained for itinerant U 5 compounds UFeGa
and USb, and they are compared with the results of the band structure calculations treating U 5 states as being itinerant. In addition, we show the results of photoemission study on some heavy fermion compounds such as UPdAl and UNiAl. The temperature dependences of the U 5 electronic structure of UPdAl will be also reported.
band states in the layered compound UFeGa observed by soft X-ray angle-resolved photoemission spectroscopyFujimori, Shinichi; Terai, Kota; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Muramatsu, Yasuji; Fujimori, Atsushi; Yamagami, Hiroshi*; Tokiwa, Yoshifumi*; Ikeda, Shugo; et al.
Physical Review B, 73(12), p.125109_1 - 125109_6, 2006/03
Times Cited Count：22 Percentile：66.94(Materials Science, Multidisciplinary)We have performed angle-resolved photoemission spectroscopy (ARPES) experiments on paramagnetic UFeGa using soft X-ray synchrotron radiation (
=500 eV) and derived the bulk- and U 5-sensitive electronic structure of UFeGa. Although the agreement between the experimental band strucure and the LDA calculation treating U 5 electrons as beeing itinerant is qualitative, the morphology of the Fermi surface is well explained by the calculation. This result claims that the importance of the electron correlation effect even for the itinerant U 5 compound.
Nishitani, Tomohiro; Nakanishi, Tsutomu*; Yamamoto, Masahiro*; Okumi, Shoji*; Furuta, Fumio*; Miyamoto, Masaharu*; Kuwahara, Makoto*; Yamamoto, Naoto*; Naniwa, Kenichi*; Watanabe, Osamu*; et al.
Journal of Applied Physics, 97(9), p.094907_1 - 094907_6, 2005/05
Times Cited Count：64 Percentile：87.25(Physics, Applied)no abstracts in English
RhGa
and UFeGaIkeda, Shugo; Okubo, Tomoyuki*; Inada, Yoshihiko*; Tokiwa, Yoshifumi; Kaneko, Koji; Matsuda, Tatsuma; Yamamoto, Etsuji; Haga, Yoshinori; Onuki, Yoshichika
Journal of Physics; Condensed Matter, 15(28), p.S2015 - S2018, 2003/07
Times Cited Count：6 Percentile：35.56(Physics, Condensed Matter)no abstracts in English
(T:Fe, Co and Pt)Ikeda, Shugo; Tokiwa, Yoshifumi*; Okubo, Tomoyuki*; Yamada, Mineko*; Matsuda, Tatsuma; Inada, Yoshihiko*; Settai, Rikio*; Yamamoto, Etsuji; Haga, Yoshinori; Onuki, Yoshichika
Physica B; Condensed Matter, 329-333(2), p.610 - 611, 2003/05
Times Cited Count：13 Percentile：55.97(Physics, Condensed Matter)no abstracts in English
Ikeda, Shugo; Tokiwa, Yoshifumi*; Haga, Yoshinori; Yamamoto, Etsuji; Okubo, Tomoyuki*; Yamada, Mineko*; Nakamura, Noriko*; Sugiyama, Kiyohiro*; Kindo, Koichi*; Inada, Yoshihiko*; et al.
Journal of the Physical Society of Japan, 72(3), p.576 - 581, 2003/03
Times Cited Count：41 Percentile：82.43(Physics, Multidisciplinary)no abstracts in English
Matsuda, Tatsuma; Haga, Yoshinori; Tokiwa, Yoshifumi; Andrei, G.; Yamamoto, Etsuji; Okubo, Tomoyuki*; Onuki, Yoshichika
Acta Physica Polonica B, 34(2), p.1071 - 1074, 2003/02
We have successfully grown a single crystal of uranium intermetallic compound URhGe. The temperature dependence of electrical resistivity shows highly anisotropic behavior. Two anomalies, which correspond to the magnetic ordering temperatures, were observed in the resistivity, magnetic susceptibility and specific heat measurements at 
= 30 K and 
=25 K. The magnetic susceptibility also shows a large uniaxial anisotropy with a magnetic easy-axis along the [010] direction.
Yamamoto, Etsuji; Haga, Yoshinori; Matsuda, Tatsuma; Inada, Yoshihiko*; Settai, Rikio*; Tokiwa, Yoshifumi*; Onuki, Yoshichika
Acta Physica Polonica B, 34(2), p.1059 - 1062, 2003/00
no abstracts in English
Haga, Yoshinori; Yamamoto, Etsuji; Tokiwa, Yoshifumi; Aoki, Dai*; Inada, Yoshihiko*; Settai, Rikio*; Maehira, Takahiro; Yamagami, Hiroshi*; Harima, Hisatomo*; Onuki, Yoshichika
Journal of Nuclear Science and Technology, 39(Suppl.3), p.56 - 62, 2002/11
Fermi surfaces of uranium compounds are investigated by de Haas-van Alphen (dHvA) effect. Band calculations well reproduce the Fermi surfaces of non-magnetic itinerant systems such as USi
, UC, UAl. Fermi surfaces of the heavy fermion compounds, where the strong correlation between carriers are important, are also explained by band calculations, except for their unusually large mass enhancement. We have also observed dHvA oscillations in the superconducting mixed states in heavy fermion superconductors such as URu
Si, UPdAl and CeRu. A significan field dependence of cyclotron effective mass and scattering life time were observed.
SiMatsuda, Tatsuma; Haga, Yoshinori; Tokiwa, Yoshifumi; Yamamoto, Etsuji; Ikeda, Shugo; Okubo, Tomoyuki*; Yamada, Mineko*; Nakamura, Akio; Onuki, Yoshichika
Journal of Nuclear Science and Technology, 39(Suppl.3), p.225 - 228, 2002/11
no abstracts in English
Tokiwa, Yoshifumi; Aoki, Dai*; Haga, Yoshinori; Yamamoto, Etsuji; Ikeda, Shugo*; Settai, Rikio*; Nakamura, Akio; Onuki, Yoshichika
Journal of the Physical Society of Japan, 70(11), p.3326 - 3330, 2001/11
Times Cited Count：15 Percentile：63.11(Physics, Multidisciplinary)We succeeded in growing a high-quality single crystal of UIn by the self-flux method and measured the electrical resistivity, magnetic susceptibility, magnetization, specific heat and de Haas-van Alphen (dHvA) oscillation. We confirmed the N
el temperature at T
= 88K from both the electrical resistivity and magnetic susceptibility measurements. We observed many dHvA branches. The Fermi surfaces are found to consist of closed Fermi surfaces and a multiply-connected Fermi surface. The cyclotron mass is relatively large, ranging from 9.8 to 33 
.
Tokiwa, Yoshifumi; Aoki, Dai*; Haga, Yoshinori; Yamamoto, Etsuji; Wi
niewski, P.*; Onuki, Yoshichika
Journal of the Physical Society of Japan, Vol.70, Supplement A, p.40 - 42, 2001/05
no abstracts in English
U M
ssbauer spectroscopic study of UX(X=Ga, P, As, Sb)Tsutsui, Satoshi; Nakada, Masami; Nasu, Saburo*; Haga, Yoshinori; Homma, Tetsuo; Yamamoto, Etsuji; Tokiwa, Yoshifumi; Aoki, Dai*; Winiewski, P.*; Onuki, Yoshichika
Journal of the Physical Society of Japan, Vol.70, Supplement A, p.34 - 36, 2001/05
no abstracts in English
