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Journal Articles

DC magnetization study on heavy-electron superconductor UBe$$_{13}$$

Shimizu, Yusei*; Haga, Yoshinori; Yanagisawa, Tatsuya*; Amitsuka, Hiroshi*; Aoki, Dai*; Brison, J.-P.*; Braithwaite, D.*

JPS Conference Proceedings (Internet), 3, p.015009_1 - 015009_6, 2014/06

Journal Articles

Thermal expansion under uniaxial pressure in URu$$_2$$Si$$_2$$

Kambe, Shinsaku; Aoki, Dai*; Salce, B.*; Bourdarot, F.*; Braithwaite, D.*; Flouquet, J.*; Brison, J.-P.*

Physical Review B, 87(11), p.115123_1 - 115123_6, 2013/03

 Times Cited Count:9 Percentile:43.08(Materials Science, Multidisciplinary)

The temperature dependence of the thermal expansion coefficient $$alpha$$ has been measured in URu$$_2$$Si$$_2$$ under uniaxial pressure $$sigma$$ along the [100] and [110] directions up to $$sim0.6$$ GPa. For both cases, the hidden order phase transition temperature $$T_0$$ increases with increasing uniaxial pressure. An anomaly $$Delta alpha$$ of the thermal expansion coefficient at $$T_0$$ appears to be enhanced under a small uniaxial pressure ($$<0.03$$ GPa). An antiferromagnetically ordered phase appears at $$T_X$$ above the critical pressure $$sigma_Xsim0.25$$ GPa for uniaxial pressure along the [100] direction, whereas no antiferromagnetic transition is detected up to $$sim0.6$$ GPa for uniaxial pressure along the [110] direction, indicating that the critical pressure is beyond $$sim0.6$$ GPa for the [110] case.

Oral presentation

Investigation on the heavy fermion superconductors by the ac heat capacity measurement

Tateiwa, Naoyuki; Haga, Yoshinori; Matsuda, Tatsuma; Ueda, Taiki*; Thamizhavel, A.*; Nakashima, Miho*; Takeuchi, Tetsuya*; Settai, Rikio*; Onuki, Yoshichika; Knebel, G.*; et al.

no journal, , 

We have developed the system for the heat capacity measurement by the thermocouple in order to study the high pressure physical properties of the rare earth and actinide compounds. In this talk, we would like to show our system and discuss our recent results on the heavy fermion superconductors CePt$$_3$$Si and UIr. It is noted that the superconductivity of UIr was found by our group. There is no inversion center in crystal structures of both compounds. The superconductivity of both compounds might be the novel type. In the case of CePt$$_3$$Si, the antiferromagnetic phase is strongly suppressed by the applied pressure and disappears above 0.6 GPa, while the superconducting phase exists in the wide pressure region up to 1.5 GPa. It is found that the overall feature of the pressure phase diagram is different from those of other heavy fermion superconductors. In the case of UIr, it is suggested by the resistivity measurement under pressures that there exists multiple ferromagnetic phases in the high pressure region. We investigated the pressure phase diagram of UIr from the thermodynamic point of view. We discuss the relation between the superconductivity and magnetism in UIr.

Oral presentation

Magnetic anisotropy and transport properties of URhSi

Matsuda, Tatsuma; Aoki, Dai*; Kotegawa, Hisashi*; Hassinger, E.*; Taufour, V.*; Knebel, G.*; Braithwaite, D.*; Salce, B.*; Yamamoto, Etsuji; Haga, Yoshinori; et al.

no journal, , 

no abstracts in English

Oral presentation

Uni-axial dependence of hidden ordering in URu$$_2$$Si$$_2$$

Kambe, Shinsaku; Aoki, Dai*; Salce, B.*; Braithwaite, D.*; Flouquet, J.*; Brison, J. P.*

no journal, , 

1 axis of the order transition temperature T0 in which URu$$_2$$Si$$_2$$ hid, and the antiferromagnetic order TN. It experimented about pressure dependence. Quality single crystal 2 (a axis) $$times$$ 2(c axis) $$times$$ 4.2(a axis) mm was used. Hidden order and antiferromagnetic order transition. In order to detect, the thermal expansion coefficient was measured using the string gauge. 1 axis pressure is Sis who can change pressure continuously at low temperature using helium gas. Tem is used and it is measurement to [100] direction (direction of 4.2 mm of a axes) 5 kbar. It carried out. Under hydrostatic pressure, although TN appeared from about 5 kbar, with the 1 axis of [100] direction pressure, it turned out that it appears from about 3 kbar. Moreover, T0 is going up. This consistents with as a result of neutron scattering. [0 01] It combines with a direction and the experimental result under hydrostatic pressure, and performs thermodynamic consideration.

Oral presentation

Thermal expansion under uniaxial pressure in URu$$_2$$Si$$_2$$, 2

Kambe, Shinsaku; Aoki, Dai*; Salce, B.*; Bourdarot, F.*; Braithwaite, D.*; Flouquet, J.*; Brison, J. P.*

no journal, , 

It experimented about the 1 axis pressure dependence of order transition temperature T$$_0$$ in which URu$$_2$$Si$$_2$$ hid, and antiferromagnetic order T$$_N$$. 2$$times$$2$$times$$4 mm of quality single crystals were used. In order to detect the hidden order and antiferromagnetic order transition, the thermal expansion coefficient was measured using the string gauge. The 1 axis pressure sigma performed measurement to [100], the [110] directions, and 0.6 GPa using the system which can change pressure continuously at low temperature using He gas. Under hydrostatic pressure, although T$$_N$$ appeared from about 0.5 GPa, with the 1 axis of [100] direction pressure, it turned out that it appears from about 0.25 GPa. Moreover, T$$_0$$ is also going up. This consistents withas a result of neutron scattering. On the other hand, in the case of [110], T$$_N$$ was not able to be observed to 0.6 GPa.

Oral presentation

Recent experimental studies in URu$$_2$$Si$$_2$$

Kambe, Shinsaku; Tokunaga, Yo; Sakai, Hironori; Aoki, Dai*; Salce, B.*; Bourdarot, F.*; Matsuda, Tatsuma*; Haga, Yoshinori; Braithwaite, D.*; Flouquet, J.*; et al.

no journal, , 

Recent two experimental investigations in URu$$_2$$Si$$_2$$ will be presented. In first part, the temperature dependence of the thermal expansion coefficient $$alpha$$ will be presented in URu$$_2$$Si$$_2$$ under uniaxial pressure $$sigma$$ along the [100] and [110] directions up to $$sim0.6$$ GPa. For both cases, the hidden order phase transition temperature $$T_0$$ increases with increasing uniaxial pressure. An antiferromagnetically ordered phase appears at $$T_X$$ above the critical pressure $$sigma_Xsim0.25$$ GPa for uniaxial pressure along the [100] direction, whereas no antiferromagnetic transition is detected up to $$sim0.6$$ GPa for uniaxial pressure along the [110] direction, indicating that the critical pressure is beyond $$sim0.6$$ GPa for the [110] case. 2-fold intrinsic (mono-domain) susceptibility anisotropy in the basal plane, a value $$sim15$$ times smaller than that obtained from recent susceptibility measurements.

Oral presentation

NMR study of ferromagnetic superconductor URhGe under uniaxial stress

Tokunaga, Yo; Aoki, Dai*; Braithwaite, D.*; Knebel, G.*; Brison, J.-P.*; Pourret, A.*; Lapertot, G.*; Niu, Q.*; Valiska, M.*; Flouquet, J.*; et al.

no journal, , 

In this study, using a single crystal of URhGe, we performed zero-field NMR study under uniaxial stress. For all the observed NMR peaks, a successive shift toward lower frequencies has been ob- served with increasing the uniaxial stress. The behavior indicates uniform and successive change of local environments at the nuclear positions. Simultaneously, however, we have also seen a broadening of the NMR peaks with increasing the stress, in particular above 0.8 GPa, suggesting the distribution of the local environments with larger stresses.

Oral presentation

NMR study of ferromagnetic superconductor URhGe under uniaxial stress

Tokunaga, Yo; Aoki, Dai*; Braithwaite, D.*; Knebel, G.*; Brison, J.-P.*; Pourret, A.*; Lapertot, G.*; Niu, Q.*; Valiska, M.*; Flouquet, J.*; et al.

no journal, , 

Recently, uniaxial stress has been found to be a remarkable tool for tuning the pairing strength in a ferromagnetic superconductor URhGe. A relatively small uniaxial stress applied along the $$b$$ crystal axis changes the superconducting (SC) phase diagram significantly, merging the low-field SC and reentrant SC domes, with a large enhancement of $$T_{sc}$$. The $$T_{sc}$$ increases both at zero field and under a field, reaching 1 K, more than twice higher than at ambient pressure. This enhancement of SC has been shown to be directly related to a change of the magnetic dimensionality, moving the system away from the Ising-type limit, which results in the rapid decrease of the $$H_{rm R}$$. In this study, by means of zero-field $$^{73}$$Ge NMR in the ferromagnetic state, we have investigated the effects of uniaxial stress on the electronic state of URhGe.

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