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Journal Articles

Ground state magnetic structure of Ce$$_2$$Ni$$_3$$Ge$$_5$$

Honda, Fuminori; Metoki, Naoto; Matsuda, Tatsuma; Haga, Yoshinori; Thamizhavel, A.*; Okuda, Yusuke*; Settai, Rikio*; Onuki, Yoshichika

Journal of Alloys and Compounds, 451(1-2), p.504 - 506, 2008/02

 Times Cited Count:6 Percentile:39.67(Chemistry, Physical)

no abstracts in English

Journal Articles

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 $$T_{rm C1}$$ 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 $$T_{rm C1}$$ was obtained in the AC-specific heat measurement.

Journal Articles

Single crystal growth and magnetic properties of antiferromagnet Ce$$_2$$Pd$$_3$$Si$$_5$$

Nguyen, D.; Haga, Yoshinori; Matsuda, Tatsuma; Yamada, Tsutomu*; Thamizhavel, A.*; Okuda, Yusuke*; Takeuchi, Tetsuya*; Sugiyama, Kiyohiro*; Hagiwara, Masayuki*; Kindo, Koichi*; et al.

Journal of the Physical Society of Japan, 76(2), p.024702_1 - 024702_6, 2007/02

 Times Cited Count:5 Percentile:37.33(Physics, Multidisciplinary)

We succeeded in growing a single crystal of Ce$$_2$$Pd$$_3$$Si$$_5$$ with the orthorhombic crystal structure by the Sn-flux method and measured the electrical resistivity, specific heat, magnetic susceptibility and magnetization. The antiferromagnetic ordering was confirmed to be $$T_{rm N}$$ = 7.2 K. The electronic specific heat coefficient was determined as 77 mJ/K$$^2cdot$$mol$$cdot$$Ce. The antiferromagnetic easy-axis was found to be the [001] direction, with an ordered moment of $$mu_{rm s}$$ = 1.3 $$mu_{rm B}$$/Ce, while [100] and [010] directions are hard-axes in magnetization. We observed a metamagnetic transition at 5.7 T for $$Hparallel$$[001] and a saturation of magnetization above 12.1 T. The characteristic magnetic phase diagram was constructed. The crystalline electric field (CEF) scheme was proposed for Ce$$_2$$Pd$$_3$$Si$$_5$$, where the splitting energies between the ground state and two excited doublets in the CEF scheme are estimated to be 87 K and 504 K, respectively.

Journal Articles

Magnetic and electrical properties in CePtSi$$_{3}$$ 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

 Times Cited Count:22 Percentile:71.12(Physics, Multidisciplinary)

We succeeded in growing a single crystal of CePtSi$$_{3}$$ by the Sn-flux method. CePtSi$$_{3}$$ 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 $$mu_{rm B}$$/Ce. The anisotropy is similar to that of CeIrSi$$_{3}$$ in which the pressure-induced superconductivity was observed.

Journal Articles

Thermodynamics Investigation on pressure-induced superconductor CeNiGe$$_3$$ by ac calorimetry

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

Journal of the Physical Society of Japan, 75(Suppl.), p.174 - 176, 2006/08

We have investigated the physical properties of Heavy Fermion superconductors by the ac calorimetry under high pressure using a thermocouple. The method is powerful tool since the high sensitive measurement of the heat capacity is possible and the precise pressure dependence of transition temperatures such as the superconducting transition can be determined. In this conference, I would like to report our investigations on the heavy fermion superconductors CePt$$_3$$Si, CeNiGe$$_3$$ and UIr. We have made pressure phase diagram of these compounds and discuss the relation between the magnetism and superconductivity.

Journal Articles

Unique magnetic properties of NdRhIn$$_5$$, TbRhIn$$_5$$, DyRhIn$$_5$$, and HoRhIn$$_5$$

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

 Times Cited Count:17 Percentile:67.3(Physics, Multidisciplinary)

We grew single crystals of NdRhIn$$_5$$, TbRhIn$$_5$$, DyRhIn$$_5$$, and HoRhIn$$_5$$ with the tetragonal crystal structure and measured the magnetic susceptibility and magnetization. NdRhIn$$_5$$ is an antiferromagnet with a Neel temperature $$T_N$$ = 11.6 K. Below $$T_N$$, 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 $$mu_B$$/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$$_5$$, DyRhIn$$_5$$ and HoRhIn$$_5$$ are found to be antiferromagnets with $$T_N$$ = 47.3, 28.1, and 15.8 K, respectively. The magnetization curves of these compounds are also quite similar to those of NdRhIn$$_5$$, revealing two metamagnetic transitions. The magnetic structures in magnetic fields are proposed by considering the exchange interactions based on the crystal structure.

Journal Articles

Fermi surface property of CeCoGe$$_3$$ and LaCoGe$$_3$$ without inversion symmetry in the tetragonal crystal structure

Thamizhavel, A.*; Shishido, Hiroaki*; Okuda, Yusuke*; Harima, Hisatomo*; Matsuda, Tatsuma; Haga, Yoshinori; Settai, Rikio*; Onuki, Yoshichika

Journal of the Physical Society of Japan, 75(4), p.044711_1 - 044711_7, 2006/06

 Times Cited Count:27 Percentile:75.21(Physics, Multidisciplinary)

We carried out the de Haas-van Alphen (dHvA) experiment of an antiferromagnet CeCoGe$$_3$$ and its reference compound LaCoGe$$_3$$ without inversion symmetry in the tetragonal crystal structure. The detected dHvA branches are similar between the two compounds. All the dHvA branches in LaCoGe$$_3$$ are well explained by the results of energy band calculations. There exist three types of compenstated Fermi surfaces. Each Fermi surface is found to consist of two types of similar Fermi surfaces, which is characteristic in the crystal structure without inversion symmetry. The main dHvA branch of LaCoGe$$_3$$ is found to possess the relatively large cyclotron mass $$m_c^*simeq$$10$$m_0$$ ($$m_0$$: rest mass of an electron), which is compared to 1m_0 in LaCoGe$$_3$$.

Journal Articles

Anisotropic magnetic properties of Ce$$_2$$Ni$$_3$$Ge$$_5$$ single crystal

Thamizhavel, A.*; Sugitani, Ichiro*; Obiraki, Yoshiko*; Nakashima, Miho*; Okuda, Yusuke*; Matsuda, Tatsuma; Haga, Yoshinori; Takeuchi, Tetsuya*; Sugiyama, Kiyohiro*; Settai, Rikio*; et al.

Physica B; Condensed Matter, 378-380, p.841 - 842, 2006/05

 Times Cited Count:0 Percentile:0(Physics, Condensed Matter)

We have succeeded in growing single crystals of Ce$$_2$$Ni$$_3$$Ge$$_5$$, which crystallizes in the orthorhombic crystal structure, by the flux method and studied the anisotropic physical properties by measuring the electrical resistivity, magnetic susceptibility and specific heat. The results of these measurements indicate that Ce$$_2$$Ni$$_3$$Ge$$_5$$ undergoes two antiferromagnetic transitions at $$T_{N1}$$=4.9 K and $$T_{N2}$$=4.3 K. The electrical resistivity and susceptibility measurements reveal strong anisotropic magnetic properties. From the specific heat measurement the electronic specific heat coefficient was found to be 90mJ/K$$^2$$mol.

Journal Articles

Pressure-induced superconductivity of Ce$$_2$$Ni$$_3$$Ge$$_5$$

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

 Times Cited Count:7 Percentile:35.16(Physics, Condensed Matter)

The N$'e$el temperature of Ce$$_2$$Ni$$_3$$Ge$$_5$$ decreases with increasing pressure $$P$$ and becomes zero at a critical pressure $$Pc sim$$ 4 Gpa. The heavy fermion state was found to be formed around $$Pc$$, in which pressure region superconductivity was found below 0.26 K.

Journal Articles

Pressure-induced heavy-fermion superconductivity in antiferromagnet CeIrSi$$_3$$ 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

 Times Cited Count:334 Percentile:98.84(Physics, Multidisciplinary)

We report the discovery of pressure-induced superconductivity in an antiferromagnet CeIrSi$$_3$$, which lacks inversion symmetry in the tetragonal crystal structure. The Neel temperature $$T_N$$ = 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 $$H_{c2}$$(0) = 11.1 T at 2.5 GPa, indicating heavy-fermion superconductivity.

Journal Articles

Fermi surface and magnetic properties of PrTIn$$_5$$ (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

 Times Cited Count:13 Percentile:59.36(Physics, Multidisciplinary)

We grew single crystals of PrCoIn$$_5$$, PrRhIn$$_5$$, and PrIrIn$$_5$$ 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$$_5$$. The cyclotron mass and/or the electronic specific heat coefficient are also approximately the same as those of LaRhIn$$_5$$. 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.

Journal Articles

Effect of pressure on electronic states in canted ferromagnet CePtAl

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

Journal of the Physical Society of Japan, 74(12), p.3393 - 3394, 2005/12

 Times Cited Count:6 Percentile:41.7(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Anisotropic magnetic properties of a pressure-induced superconductor Ce$$_2$$Ni$$_3$$Ge$$_5$$

Thamizhavel, A.*; Nakashima, Hiroshi*; Obiraki, Yoshiko*; Nakashima, Miho*; Matsuda, Tatsuma; Haga, Yoshinori; Sugiyama, Kiyohiro*; Takeuchi, Tetsuya*; Settai, Rikio*; Hagiwara, Masayuki*; et al.

Journal of the Physical Society of Japan, 74(10), p.2843 - 2848, 2005/10

 Times Cited Count:13 Percentile:59.36(Physics, Multidisciplinary)

Single crystals of a pressure-induced superconductor Ce$$_2$$Ni$$_3$$Ge$$_5$$ have been successfully grown by the flux method. The anisotropic magnetic properties due to the orthorhombic crystal structure have been studied precisely by the electrical resistivity, specific heat, magnetic susceptibility, and high-field magnetization measurements. The results of these measurements confirmed two antiferromagnetic transitions at T$$_{N1}$$=5.0 K and T$$_{N2}$$=4.3 K. The electronic specific heat coefficient obtained from the low-temperature specific heat data amounts to 90 mJ/K$$^2$$mol Ce. The high-field magnetization for H //[100] shows four magnetic transitions at 11.8, 12.9, 17.5 and 23.9 T with a saturation moment of 0.73 $$mu_B$$/Ce at 1.3 K. We have also performed the crystalline electric field (CEF) analysis on the magnetic susceptibility and magnetization to understand the magnetocrystalline anisotropy, where the splitting energies of two excited doublets in the CEF scheme are estimated to be 140 and 576 K, respectively.

Journal Articles

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

 Times Cited Count:14 Percentile:61.04(Physics, Multidisciplinary)

Journal Articles

Crystalline electric field excitations in CeAgSb$$_{2}$$

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

Journal of Physics; Condensed Matter, 15(23), p.S2179 - S2182, 2003/07

no abstracts in English

Journal Articles

Crystal structure, magnetic ordering, and magnetic excitation in the 4${it f}$-localized ferromagnet CeAgSb$$_{2}$$

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

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

 Times Cited Count:44 Percentile:84.48(Materials Science, Multidisciplinary)

no abstracts in English

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

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 CePt$$_3$$Si with the non-centrosymmetric tetragonal structure. Superconductivity with the transition temperature $$T_{rm sc}$$=0.75K is realized in the long-range antiferromagnetic ordered state with the N$'e$el temperature $$T_{rm N}$$=2.2K. We determine the pressure phase diagram of CePt$$_3$$Si. The N$'e$el temperature decreases with increasing pressure and becomes zero at the critical pressure $$P_{rm AF}$$$$simeq$$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 $$gamma$$ around $$P_{rm AF}$$. This suggests that the superconductivity in CePt$$_3$$Si differs from those observed around the quantum critical point such as in CeIn$$_3$$.

Oral presentation

Magnetic structures in Ce$$_2$$Ni$$_3$$Ge$$_5$$

Honda, Fuminori; Metoki, Naoto; Matsuda, Tatsuma; Haga, Yoshinori; Thamizhavel, A.*; Okuda, Yusuke*; Settai, Rikio*; Onuki, Yoshichika

no journal, , 

no abstracts in English

Oral presentation

Multi-step magnetic transition in non-centrosymmetric compound CeCoGe$$_3$$

Kaneko, Koji; Metoki, Naoto; Takeuchi, Tetsuya*; Matsuda, Tatsuma; Haga, Yoshinori; Thamizhavel, A.*; Settai, Rikio*; Onuki, Yoshichika

no journal, , 

We report neutron diffraction studies on non-centrosymmetric compound CeCoGe$$_3$$ with the BaNiSn$$_3$$-type structure. Upon cooling down the temperature, emergence of the 1,0,1/3 magnetic reflection was found below 20,K. The 1,0,/4 reflection appears below 8,K substituting 1,0,1/3, and finally 1,0,,1/2 reflection appears below 5.3,K. This result indicates that the multi-step transition in CeCoGe$$_3$$ is the change of the periodicity along the c-axis.

21 (Records 1-20 displayed on this page)