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Sn wires with and without Cu-Nb reinforcementNakamoto, Mio*; Sugano, Michinaka*; Ogitsu, Toru*; Sugimoto, Masahiro*; Taniguchi, Ryo*; Hirose, Kiyoshige*; Kawasaki, Takuro; Gong, W.; Harjo, S.; Awaji, Satoshi*; et al.
IEEE Transactions on Applied Superconductivity, 34(5), p.8400806_1 - 8400806_6, 2024/08
Times Cited Count：0 Percentile：0.00(Engineering, Electrical & Electronic)
Tokiwa, Yoshifumi; Opletal, P.; Sakai, Hironori; Kambe, Shinsaku; Yamamoto, Etsuji; Kimata, Motoi*; Awaji, Satoshi*; Sasaki, Takahiko*; Aoki, Dai*; Haga, Yoshinori; et al.
Physical Review B, 109(14), p.L140502_1 - L140502_6, 2024/04
Times Cited Count：1 Percentile：56.34(Materials Science, Multidisciplinary)The normal-conducting state of the superconductor UTe is studied by entropy analysis for magnetic fields along the 
-axis, obtained from magnetization using the relation 
. We observe a strong increase in entropy with magnetic field due to metamagnetic fluctuations (spatially uniform, 
). The field dependence is well described by the Hertz-Millis-Moriya theory for quantum criticality of itinerant metamagnetism. Notably, the lower bound of the quantum-critical region coincides well with the position of the minimum in the superconducting transition temperature 
. Hence, our results suggest that fluctuations reinforce the superconductivity.
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：4 Percentile：52.62(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.
along hard magnetic axisSakai, Hironori; Tokiwa, Yoshifumi; Opletal, P.; Kimata, Motoi*; Awaji, Satoshi*; Sasaki, Takahiko*; Aoki, Dai*; Kambe, Shinsaku; Tokunaga, Yo; Haga, Yoshinori
Physical Review Letters, 130(19), p.196002_1 - 196002_6, 2023/05
Times Cited Count：18 Percentile：96.06(Physics, Multidisciplinary)The superconducting (SC) phase diagram in uranium ditelluride is explored under magnetic fields (
) along the hard magnetic -axis using a high-quality single crystal with 
= 2.1 K. Simultaneous electrical resistivity and AC magnetic susceptibility measurements discern low- and high-field SC (LFSC and HFSC, respectively) phases with contrasting field-angular dependence. Crystal quality increases the upper critical field of the LFSC phase, but the 
of 
T, at which the HFSC phase appears, is always the same through the various crystals. A phase boundary signature is also observed inside the LFSC phase near , indicating an intermediate SC phase characterized by small flux pinning forces.
MnSiShigeta, Iduru*; Oku, Shuta*; Kubota, Takahide*; Kimura, Shojiro*; Seki, Takeshi*; Shinozaki, Bunju*; Awaji, Satoshi*; Takanashi, Koki; Hiroi, Masahiko*
AIP Advances (Internet), 13(2), p.025116_1 - 025116_5, 2023/02
Times Cited Count：0 Percentile：0.00(Nanoscience & Nanotechnology)Awaji, Satoshi*; Namba, Masashi*; Watanabe, Kazuo*; Kai, Hideki*; Mukaida, Masashi*; Okayasu, Satoru
Journal of Applied Physics, 111(1), p.013914_1 - 013914_4, 2012/01
Times Cited Count：26 Percentile：69.58(Physics, Applied)The effect of 
-axis correlated pinning on the critical current density 
at low temperatures under high magnetic fields was investigated on the basis of the transport measurements of and irreversibility field B
properties of an ErBaCuO
film with inclined columnar defects. The contribution of correlated pinning on decreased drastically with decreasing temperature under high magnetic fields above the matching field. At low temperatures, the presence of a matching field limited the pinning force for correlated pinning, while the ratio of the maximum pinning force of the correlated pinning to the random one was proportional to the inverse of B. In order to improve the critical current properties at low temperatures under high magnetic fields, an increase in the matching field and/or the introduction of strong random pinning are effective.
Awaji, Satoshi*; Namba, Masashi*; Watanabe, Kazuo*; Ito, Shun*; Aoyagi, Eiji*; Kai, Hideki*; Mukaida, Masashi*; Okayasu, Satoru
IEEE Transactions on Applied Superconductivity, 21(3), p.3192 - 3195, 2011/06
Times Cited Count：5 Percentile：33.23(Engineering, Electrical & Electronic)The flux pinning behaviors for the heavy ion irradiated Er123 films are investigated based on the detailed 
(
, 
, 
) properties. The double peaks of 
curves for //c appear in case of the matching field of 0.3 T along -axis and 1.7 T tilted from -axis. In addition, the peaks on () at = 0
(B//c), which originate from the columnar defects, decrease with increasing magnetic field but increase again near the irreversibility field. We found that the cooperation model of the -axis correlated and random pinning centers can describe the observed double peak behavior of (B) and the angular dependence of related to the correlated pinning.
Ito, Takayoshi; Harjo, S.; Osamura, Kozo*; Hemmi, Tsutomu; Awaji, Satoshi*; Machiya, Shutaro*; Oguro, Hidetoshi*; Nishijima, Gen*; Takahashi, Koki*; Matsui, Kunihiro; et al.
Materials Science Forum, 681, p.209 - 214, 2011/05
Times Cited Count：1 Percentile：51.29(Materials Science, Multidisciplinary)Iigaki, Kazuhiko; Sakaba, Nariaki; Kawaji, Satoshi; Iyoku, Tatsuo
Transactions of 16th International Conference on Structural Mechanics in Reactor Technology (SMiRT-16) (CD-ROM), 7 Pages, 2001/08
no abstracts in English
Saito, Kenji; Homma, Fumitaka; Omata, Toru; Aono, Tetsuya; Kawaji, Satoshi; Kawasaki, Kozo; Iyoku, Tatsuo
Proceedings of International Topical Meeting on Nuclear Plant Instrumentation, Controls, and Human-Machine Interface Technologies (NPIC&HMIT 2000) (CD-ROM), 8 Pages, 2000/00
no abstracts in English
Tachibana, Yukio; Kunitomi, Kazuhiko; ; Sawa, Kazuhiro; Takeda, Takeshi; Saikusa, Akio; Kawaji, Satoshi; Iyoku, Tatsuo
JAERI-Tech 98-027, 74 Pages, 1998/07
no abstracts in English
Sakaba, Nariaki; Iigaki, Kazuhiro; Kawaji, Satoshi; Iyoku, Tatsuo
JAERI-Tech 98-013, 152 Pages, 1998/03
no abstracts in English
Baba, Osamu; Kunitomi, Kazuhiko; Kawaji, Satoshi; Tanaka, Toshiyuki; Shiozawa, Shusaku; Okubo, Minoru
Proc. of ASME
JSME 4th Int. Conf. on Nuclear Engineering 1996 (ICONE-4), 2, p.281 - 287, 1996/00
no abstracts in English
Shimomura, Hiroaki; Kawaji, Satoshi; Ota, Yukimaru
Proc. of the 2nd Int. Symp. on Magnetic Bearings, p.93 - 99, 1990/00
no abstracts in English
Shimomura, Hiroaki; Kawaji, Satoshi
Proc. of the IAEA Specialists' Meeting on Communication and Data Transfer in NPP, 17 Pages, 1990/00
no abstracts in English
Shimomura, Hiroaki; Kawaji, Satoshi; Fujisaki, Katsuo;
JAERI-M 89-064, 90 Pages, 1989/06
no abstracts in English
Shimomura, Hiroaki; Kawaji, Satoshi; Fujisaki, Katsuo;
Gas-Cooled Reactor Coolant Circulator and Blower Technology, p.148 - 156, 1988/00
no abstracts in English
Harjo, S.; Aizawa, Kazuya; Ito, Takayoshi; Osamura, Kozo*; Awaji, Satoshi*; Hemmi, Tsutomu; Machiya, Shutaro*; Tsuchiya, Yoshinori*; Matsui, Kunihiro; Nishijima, Gen*
no journal, ,
no abstracts in English
Tokiwa, Yoshifumi; Opletal, P.; Sakai, Hironori; Yamamoto, Etsuji; Kambe, Shinsaku; Tokunaga, Yo; Haga, Yoshinori; Kimata, Motoi*; Awaji, Satoshi*; Sasaki, Takahiko*; et al.
no journal, ,
In unconventional superconductors, there are cases of vortex liquid-like state. When the pinning is strong, vortices do not move, and thus, the formation of such abnormal states requires pure and pristine crystals. Recently, the growth of pure single crystals of the spin-triplet superconductor UTe using a molten salt flux has been reported. In this study, we report research on vortices in UTe using such pure single crystals. As a result, in the magnetic field range of 15 T to 22 T, the critical current showed a maximum in temperature dependence, and a low-temperature region with a low critical current was observed deep in the superconducting state. This low critical current region matches the recently reported intermediate field superconducting phase. This suggests a weakening of the pinning force and a decrease in the critical current in the intermediate field superconducting phase.
Tokiwa, Yoshifumi; Opletal, P.; Sakai, Hironori; Yamamoto, Etsuji; Kambe, Shinsaku; Tokunaga, Yo; Haga, Yoshinori; Kimata, Motoi*; Awaji, Satoshi*; Sasaki, Takahiko*; et al.
no journal, ,
In unconventional superconductivity, magnetism is considered to be the origin of the superconducting interaction, and the relationship between magnetism and superconductivity is a central theme of research. UTe has attracted much attention due to its potential for reentrant superconductivity and spin-triplet superconductivity in magnetic fields. In this material, when a magnetic field is applied along the a-axis, a weak metamagnetism occurs near 6T due to Fermi surface instability. In the initial crystals synthesized by the vapor phase epitaxy, superconductivity disappeared in the magnetic field where metamagnetism was generated because 
= 1.6K and upper critical magnetic field 
= 6T, and superconductivity was not affected. In the pure single crystal synthesized by the molten salt flux method, =2.1K is 25% stronger than the initial while =12T is doubled. In this study, we revealed that this metamagnetism enhances .
