Pressure effect of electrical resistivity and AC specific heat in CePtAl

Nakashima, Miho*; Ueda, Taiki*; Shimizu, Katsuya*; Nakashima, Hiroshi*; Thamizhavel, A.*; Tateiwa, Naoyuki; Haga, Yoshinori; Hedo, Masato*; Uwatoko, Yoshiya*; Settai, Rikio*; et al.

Journal of Magnetism and Magnetic Materials, 310(2, Part1), p.e9 - e11, 2007/03

We measured the electrical resistivity and AC-specific heat for a canted ferromagnet CePtAl under pressures using a diamond-anvilpressure cell. With increasing pressure, the magnetic ordering temperature increases monotonously, becomes constant above 8 GPa and then starts to decrease steeply in a narrow pressure region from 10.3 to 10.9 GPa, indicating the first-order like phase transition. The similar pressure dependence of was obtained in the AC-specific heat measurement.

Magnetic and electrical properties in CePtSi without inversion symmetry in the crystal structure

Kawai, Tomoya*; Okuda, Yusuke*; Shishido, Hiroaki*; Thamizhavel, A.*; Matsuda, Tatsuma; Haga, Yoshinori; Nakashima, Miho*; Takeuchi, Tetsuya*; Hedo, Masato*; Uwatoko, Yoshiya*; et al.

Journal of the Physical Society of Japan, 76(1), p.014710_1 - 014710_6, 2007/01

https://doi.org/10.1143/JPSJ.76.014710

We succeeded in growing a single crystal of CePtSi by the Sn-flux method. CePtSi is found to be an antiferromagnet with two transitions at 4.8 and 2.4 K. Magnetic easy direction was [100] direction with an ordered moment of 1.15 /Ce. The anisotropy is similar to that of CeIrSi in which the pressure-induced superconductivity was observed.

Unique magnetic properties of NdRhIn, TbRhIn, DyRhIn, and HoRhIn

Hieu, N. V.*; Shishido, Hiroaki*; Takeuchi, Tetsuya*; Thamizhavel, A.*; Nakashima, Hiroshi*; Sugiyama, Kiyohiro*; Settai, Rikio*; Matsuda, Tatsuma; Haga, Yoshinori; Hagiwara, Masayuki*; et al.

Journal of the Physical Society of Japan, 75(7), p.074708_1 - 074708_6, 2006/07

https://doi.org/10.1143/JPSJ.75.074708

We grew single crystals of NdRhIn, TbRhIn, DyRhIn, and HoRhIn with the tetragonal crystal structure and measured the magnetic susceptibility and magnetization. NdRhIn is an antiferromagnet with a Neel temperature = 11.6 K. Below , magnetization reveals two metamagnetic transitions at Hm1 = 70 kOe and Hm2 = 93 kOe for the magnetic field along the [001] direction. The saturation moment of 2.5 /Nd is in good agreement with the staggered Nd moment determined by the neutron diffraction experiment. These metamagnetic transitions correspond to the change of the magnetic structure. TbRhIn, DyRhIn and HoRhIn are found to be antiferromagnets with = 47.3, 28.1, and 15.8 K, respectively. The magnetization curves of these compounds are also quite similar to those of NdRhIn, revealing two metamagnetic transitions. The magnetic structures in magnetic fields are proposed by considering the exchange interactions based on the crystal structure.

Pressure-induced superconductivity of CeNiGe

Nakashima, Miho*; Kohara, Hisanori*; Thamizhavel, A.*; Matsuda, Tatsuma; Haga, Yoshinori; Hedo, Masato*; Uwatoko, Yoshiya*; Settai, Rikio*; Onuki, Yoshichika

Physica B; Condensed Matter, 378-380, p.402 - 403, 2006/05

https://doi.org/10.1016/j.physb.2006.01.063

The Nel temperature of CeNiGe decreases with increasing pressure and becomes zero at a critical pressure 4 Gpa. The heavy fermion state was found to be formed around , in which pressure region superconductivity was found below 0.26 K.

Pressure-induced heavy-fermion superconductivity in antiferromagnet CeIrSi without inversion symmetry

Sugitani, Ichiro*; Okuda, Yusuke*; Shishido, Hiroaki*; Yamada, Tsutomu*; Thamizhavel, A.*; Yamamoto, Etsuji; Matsuda, Tatsuma; Haga, Yoshinori; Takeuchi, Tetsuya*; Settai, Rikio*; et al.

Journal of the Physical Society of Japan, 75(4), p.043703_1 - 043703_4, 2006/04

https://doi.org/10.1143/JPSJ.75.043703

We report the discovery of pressure-induced superconductivity in an antiferromagnet CeIrSi, which lacks inversion symmetry in the tetragonal crystal structure. The Neel temperature = 5.0 K at ambient pressure decreases monotonically with increasing pressure, and becomes zero at about 2.5 GPa. Superconductivity appears in a wide pressure region from 1.8 GPa to about 3.5 GPa, with a relatively large superconduting transition temperature Tsc= 1.6 K and a large upper critical field (0) = 11.1 T at 2.5 GPa, indicating heavy-fermion superconductivity.

Fermi surface and magnetic properties of PrTIn (T: Co, Rh, and Ir)

Hieu, N. V.*; Shishido, Hiroaki*; Thamizhavel, A.*; Settai, Rikio*; Araki, Shingo*; Nozue, Yasuo*; Matsuda, Tatsuma; Haga, Yoshinori; Takeuchi, Tetsuya*; Harima, Hisatomo*; et al.

Journal of the Physical Society of Japan, 74(12), p.3320 - 3328, 2005/12

https://doi.org/10.1143/JPSJ.74.3320

We grew single crystals of PrCoIn, PrRhIn, and PrIrIn with the tetragonal crystal structure and measured the electrical resistivity, specific heat, magnetic susceptibility, magnetization and de Haas-van Alphen effect. These Pr compounds reveal no magnetic ordering. The topology of the Fermi surfaces is the same as that of a non-4 f reference compound LaRhIn. The cyclotron mass and/or the electronic specific heat coefficient are also approximately the same as those of LaRhIn. The magnetic susceptibility and magnetization are anisotropic, reflecting the crystal structure, which are well explained by the tetragonal crystalline electric field scheme with the singlet ground state.

Magnetic property and pressure effect of a single crystal CeRhGe

Ueda, Taiki*; Honda, Daisuke*; Shiromoto, Tomoyuki*; Metoki, Naoto; Honda, Fuminori*; Kaneko, Koji; Haga, Yoshinori; Matsuda, Tatsuma; Takeuchi, Tetsuya*; Thamizhavel, A.*; et al.

Journal of the Physical Society of Japan, 74(10), p.2836 - 2842, 2005/10

https://doi.org/10.1143/JPSJ.74.2836

Crystal structure, magnetic ordering, and magnetic excitation in the 4-localized ferromagnet CeAgSb

Araki, Shingo; Metoki, Naoto; Galatanu, A.; Yamamoto, Etsuji; Thamizhavel, A.*; Onuki, Yoshichika

Physical Review B, 68(2), p.024408_1 - 024408_9, 2003/07

https://doi.org/10.1103/PhysRevB.68.024408

no abstracts in English

Thermodynamics study on the heavy fermion superconductor under high pressure

Tateiwa, Naoyuki; Haga, Yoshinori; Matsuda, Tatsuma; Ikeda, Shugo; Nakashima, Miho*; Thamizhavel, A.*; Takeuchi, Tetsuya*; Settai, Rikio*; Onuki, Yoshichika

no journal, , 

I will show our recent investigations on the heavy femion superconductors by the ac calorimetry method under pressure. The method is powerful tool since the high sensitive measurement of the heat capacity is possible. I will present our study on superconductivity in CePtSi with the non-centrosymmetric tetragonal structure. Superconductivity with the transition temperature =0.75K is realized in the long-range antiferromagnetic ordered state with the Nel temperature =2.2K. We determine the pressure phase diagram of CePtSi. The Nel temperature decreases with increasing pressure and becomes zero at the critical pressure 0.6GPa. On the other hand, the superconducting phase exists in a wider pressure region from ambient pressure to about 1.5 GPa. There is no anomalous singular behavior in the pressure dependences of the electronic specific heat coefficient around . This suggests that the superconductivity in CePtSi differs from those observed around the quantum critical point such as in CeIn.

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 CePtSi 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 CePtSi, 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.