Mineko Yamada

Quasi-two Dimensional Electronic State of the Antiferromagnet UPtGa5

We have carried out the de Haas–van Alphen (dHvA) experiment to clarify the Fermi surface property of an antiferromagnet UPtGa 5 , and have constructed the magnetic phase diagram from the high-fiel...

Electrical and Magnetic Properties of a Single Crystal UCu2Si2

We have succeeded in growing a high-quality single crystal of UCu 2 Si 2 with the tetragonal structure by the Sn-flux method and measured the electrical resistivity, magnetic susceptibility, magnetization and specific heat. UCu 2 Si 2 is found to order antiferromagnetically below T N =106 K, and follows a successive ferromagnetic ordering at T C =100 K. The magnetic properties are highly anisotropic, reflecting the crystal structure. An easy-axis of magnetization is found to be the [001] direction ( c -axis) both in the antiferromagnetic and ferromagnetic phases, while the [100] direction ( a -axis) corresponds to the hard-axis in magnetization. The magnetization curve in the antiferromagnetic phase indicates a clear metamagnetic transition at a low field of about 1 kOe and changes into a ferromagnetic magnetization curve below T C =100 K. The saturation moment is determined as 1.75 µ B /U at 2 K. The electronic specific heat coefficient is also determined as 20 mJ/(K 2 ·mol).

Electronic, Magnetic and Superconducting Properties of Quasi-two Dimensional Compounds Ce2RhIn8 and La2RhIn8

We have measured the electrical resistivity, magnetic susceptibility, high-field magnetization, specific heat and de Haas–van Alphen (dHvA) oscillation of Ce 2 RhIn 8 , together with the dHvA oscillation of La 2 RhIn 8 . In La 2 RhIn 8 we detected three kinds of dHvA branches showing cylindrical Fermi surfaces, which are well explained by the result of FLAPW energy band calculations. The corresponding two dHvA branches were detected in Ce 2 RhIn 8 , indicating that the topology of the Fermi surface in Ce 2 RhIn 8 is approximately the same as that of La 2 RhIn 8 . The magnetic susceptibility and magnetization of Ce 2 RhIn 8 were analyzed on the basis of the crystalline electric field scheme of localized-4 f energy levels. Pressure-induced superconductivity was confirmed above 1.2 GPa from the resistivity and ac-susceptibility measurements.

Low Temperature Magnetic Properties of CeTBi2 (T: Ni, Cu and Ag) Single Crystals

A series of the ternary compounds CeTBi 2 (T: Ni, Cu and Ag) have been grown in the single crystalline form by means of the flux method. These compounds crystallize in the tetragonal crystal struct...

Huge residual resistivity in the quantum critical region of CeAgSb2

We have studied the effect of pressure on the electrical resistivity of a high-quality single crystal CeAgSb2 which has a small net ferromagnetic moment of 0.4μB/Ce. The magnetic ordering temperature Tord = 9.7 K decreases with increasing pressure p and disappears at a critical pressure pc 3.3 GPa. The residual resistivity, which is close to zero up to 3 GPa, increases steeply above 3 GPa, reaching 55μΩ cm at pc. A huge residual resistivity is found to appear when the magnetic order disappears.

Magnetic and Fermi surface properties of UTGa5 (T: Fe, Co and Pt)

We succeeded in growing high-quality single crystals of UTGa5 (T: Fe, Co and Pt) by the self-flux method, and measured the de Haas–van Alphen effect. With increasing the number of 3d-electrons, from Fe to Pt, the Fermi surface is found to change systematically, indicating cylindrical Fermi surfaces in UFeGa5 and UPtGa5.

Electrical and magnetic properties of the cerium–transition metal intermetallics CeTSb2 (T: Cu, Au, Ni)

We have succeeded in growing single crystals of the cerium–transition metal intermetallics CeTSb2 (T: Cu, Au, Ni) with the tetragonal structure via the self-flux method, and measured the electrical resistivity, magnetic susceptibility, magnetization and specific heat. CeCuSb2 and CeAuSb2 are antiferromagnets with N! eel temperatures of 6.9 and 5.0 K, respectively. CeCuSb2 is a heavy-fermion antiferromagnet with an electronic specific heat coefficient g ¼ 200 mJ/ K 2 mol. CeAuSb2 also is a similar compound with an antiferromagnetic easy axis along the [0 0 1] direction. CeNiSb2 is a ferromagnet with a Curie temperature of 6.0 K. The easy axis is oriented along [1 0 0], with a moment of 0.6mB/Ce. r 2002 Elsevier Science B.V. All rights reserved.

On the unusual magnetic behaviour of CeRh3B2

CeRh3B2 is a ferromagnet with an unexpectedly high Curie temperature and low saturation magnetic moments. The origin of its unusual magnetic behaviour remains unelucidated despite various investigations performed in the last two decades. Here we present magnetic results obtained on high-quality single crystals over a wide temperature range. Some new magnetic features are uncovered and possible approaches to explaining its magnetism are briefly discussed.

An unusual hollow cylindrical Fermi surface of a quasi-two-dimensional compound CeAgSb2

Abstract We have carried out the de Haas-van Alphen (dHvA) experiment, together with electrical resistivity, magnetic susceptibility, magnetization and specific heat experiments on a high-quality single-crystal CeAgSb2, which has a small net ferromagnetic moment of 0.4 μB per Ce atom. The bulk magnetic properties are well explained by the crystalline electric field scheme. On the other hand, large dHvA frequencies of 108 Oe, which correspond to cylindrical Fermi surfaces, were detected by the dHvA measurement for the magnetic field along the tetragonal [001] direction, indicating the quasi-two-dimensional electronic structure. The dHvA branches of CeAgSb2 are highly different from those with small dHvA frequencies of 107 Oe for the reference compounds LaAgSb2 and YAgSb2 which exhibit a semimetallic character. The dHvA results have been compared with the results of the energy band calculations. It was concluded that the 4f electron is mainly localized and that the Fermi surface of CeAgSb2 is similar to that of LaAgSb2, but it is slightly enlarged so as to form the large orbits along a hollow cylindrical Fermi surface.

de Haas-van Alphen effect and magnetoresistance in CeRh3B2

Abstract CeRh3B2 has the highest Curie temperature of 120 K in the cerium compounds, with a saturation moment of about 0.4μB/Ce. We have succeeded in growing high-quality single crystals of CeRh3B2, and measured the de Haas-van Alphen (dHvA) effect and the transverse magnetoresistance to clarify the 4f-electronic state. The dHvA frequencies are found to be in the range from 0.4– 2 kT with the cyclotron mass of 1.7– 2.4 m 0 . The magnetoresistance suggests the existence of open orbits on the Fermi surface.