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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:0The 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.
Sakai, 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:5 Percentile:92.42(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.
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:25 Percentile:69.54(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:33.75(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:52.78(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 ASMEJSME 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
Harjo, S.; Aizawa, Kazuya; Ito, Takayoshi*; Abe, Jun; Osamura, Kozo*; Hemmi, Tsutomu; Jin, X.*; Nakamoto, Tatsushi*; Awaji, Satoshi*; Takahashi, Koki*
no journal, ,
Sakai, Hironori; Higa, Nonoka; Hattori, Taisuke; Tokunaga, Yo; Haga, Yoshinori; Kambe, Shinsaku; Goto, Takayuki*; Hirata, Michihiro*; Awaji, Satoshi*; Sasaki, Takahiko*
no journal, ,
We have performed Si nuclear magnetic resonance (NMR) experiments using single crystal of strongly correlated electrons system URuSi under high external field of about 24 T. The temperature dependence of NMR shift in the paramagnetic state varies with external fields. The temperature and field dependences of NMR shifts resembles those of magnetic susceptibility.
Tokiwa, Yoshifumi; Opletal, P.; Sakai, Hironori; Yamamoto, Etsuji; Kambe, Shinsaku; Tokunaga, Yo; Haga, Yoshinori; Kimata, Motoi*; Awaji, Satoshi*; Sasaki, Takahiko*; et al.
no journal, ,
UTe has attracted much attention due to the possibility of reentrant superconductivity and spin triplet superconductivity in a magnetic field. In this material, when a magnetic field is applied in the b-axis direction, Tc decreases once due to the magnetic field, but Tc increases under a magnetic field of about 16T or more. In this field direction, there is a metamagnetic transition at 34T. The relationship between this metamagnetism and the anomalous enhancement of Tc has been discussed. Many unconventional superconductors exhibit an unusual metallic state in the normal phase. It is believed that magnetic fluctuations, which are the cause of this phenomenon, generate superconducting electron pairs. Entropy is a direct measure of fluctuations, as entropy exhibits a maximum at the quantum critical point. Therefore, the relationship between fluctuations and superconductivity can be clarified by entropy measurements in the normal state. In this study, we performed precise magnetization measurements at temperatures up to 2 K and magnetic fields up to 24 T using cryogen-free superconducting magnets at the Research Center for High Magnetic Field Superconducting Materials, IMR, Tohoku University. We used a thermodynamic relation to map the entropy in the magnetic field-temperature parameter space. In this talk, we discuss the relationship between the entropy increase due to metamagnetic fluctuations and superconductivity.
Haga, Yoshinori; Sakai, Hironori; Opletal, P.; Tokiwa, Yoshifumi; Yamamoto, Etsuji; Kambe, Shinsaku; Tokunaga, Yo; Kimata, Motoi*; Nakamura, Shintaro*; Awaji, Satoshi*; et al.
no journal, ,
no abstracts in English
Sakai, Hironori; Tokiwa, Yoshifumi; Opletal, P.; Kimata, Motoi*; Awaji, Satoshi*; Sasaki, Takahiko*; Aoki, Dai*; Kambe, Shinsaku; Tokunaga, Yo; Haga, Yoshinori
no journal, ,
For a paramagnetic superconductor UTe, a "field-reionforced superconducting state" in which increases with magnetic field above 15 T emerges when a magnetic field is applied "exactly" in the direction of the magnetically hard axis. In order to investigate this high-field superconducting phase, we have attempted to determine the magnetic field-temperature phase diagram of ultra-clean single crystals using a cryogen-free 25 T superconducting magnet (25T-CSM) at the High Field Laboratory for Superconducting Materials, Institute for Materials Research, Tohoku University. In this presentation, we will report the obtained results.