Kazuyuki Motoki

Metamagnetic Transition in PrCu2 Studied by the de Haas-van Alphen Effect

We have observed a metamagnetic transition in PrCu 2 where a cooperative Jahn-Teller effect occurs below 8 K. This transition brings about a conversion between an easy and a hard axes in magnetization, which is reflected in a drastic change of the de Haas-van Alphen amplitude, that is a change of the scattering lifetime of conduction electrons. The origin of the metamagnetic transition is ascribed to a quadrupole moment of the 4 f level.

Magnetic properties of single crystal CeFe2Ge2

Abstract We have grown a single crystal of CeFe 2 Ge 2 by a Czochralski pulling method in a tetra-arc furnace. The electrical resistivity and magnetic susceptibility are highly anisotropic, which is similar to CeRu 2 Si 2 . The electronic specific heat coefficient is 210 mJ/K 2 mol, indicating a heavy electron system with a non-magnetic ground state. These experimental results, including the magnetoresistance, are compared to those of LaFe 2 Ge 2 .

Magnetoresistance and de Haas-van Alphen Effect in YbGa2

We have succeeded in growing a high-quality single crystal of YbGa 2 , and have done the magnetoresistance and the de Haas-van Alphen experiments. YbGa 2 is a semimetal and Fermi surfaces consist of the closed electron and hole ones. Their cyclotron masses are in the range of 0.2 to 0.9 m 0 .

De Haas-van Alphen studies of rare earth compounds

Abstract The de Haas-van Alphen amplitude of branch d in CeIn3 is reduced with oscillation by three orders of magnitude when the field is tilted from 〈100〉 to 〈110〉 in the {100} plane. This is explained by considering the angular dependence of the cyclotron mass and the electron spin g-factor.

Metamagnetic transition in PrCu2

Abstract We have observed a metamagnetic transition in PrCu 2 where there is a cooperative Jahn-Teller effect occurring below 8 K. This transition brings about a large crystal distortion and also a drastic change of the electronic state, namely the Fermi surface.

Fermi surfaces of YRu2Si2 and LaRu2Si2

Abstract We have measured the de Haas-van Alphen effect of YRu 2 Si 2 and LaRu 2 Si 2 to clarify the Fermi surfaces and cyclotron masses. Main hole-Fermi surfaces of both compounds with a distorted ellipsoid shape are similar, occupying about half of the Brillouin zone. The small hole-Fermi surfaces with the shape of a rugby ball are three in number for LaRu 2 Si 2 , and one for YRu 2 Si 2 . An electron-Fermi surface consists of a doughnut like shape for LaRu 2 Si 2 , while a cylinder along the [0 0 1] direction and a multiply-connected shape exist for YRu 2 Si 2 . The cyclotron masses of YRu 2 Si 2 are a little larger than those of LaRu 2 Si 2 .

de Haas-van Alphen Effect in LaAg and CeAg.

We have observed the de Haas-van Alphen oscillation in LaAg and CeAg. Four kinds of closed Fermi surfaces are detected in LaAg, which are in good agreement with the results of band calculations. In CeAg, each Fermi surface is split into two Fermi surfaces with the up- and down-spin states due to the ferromagnetic exchange interaction. The cyclotron mass of CeAg is not very large, which is only by 40% larger than the corresponding mass of LaAg.

Transport Properties in LaAg and CeAg Single Crystals.

We have measured the Hall effect, magnetoresistance, thermoelectric power, magnetic susceptibility and magnetization in CeAg and LaAg single crystals. We observed clear anomalies related with a ferromagnetic transition at 5.5 K and a quadrupolar ordering at 17 K both in the Hall effect and magnetic susceptibility for CeAg.

Magnetoresistance and de Haas-van Alphen Effect in YRu2Si2.

We have measured the magnetoresistance and the de Haas-van Alphen effect of YRu 2 Si 2 . The Fermi surface and cyclotron mass of YRu 2 Si 2 are compared to those of LaRu 2 Si 2 and LaRu 2 Ge 2 . Main hole Fermi surfaces of the three compounds are similar and ellipsoidal in shape, which occupy about half of the Brillouin zone. The small hole Fermi surface with a shape of rugby ball is one in number for YRu 2 Si 2 , while three for LaRu 2 Si 2 and LaRu 2 Ge 2 . A cylindrical Fermi surface and a multiply-connected Fermi surface exist for YRu 2 Si 2 , while there exists a doughnut like electron Fermi surface for LaRu 2 Si 2 and LaRu 2 Ge 2 . The cyclotron masses of YRu 2 Si 2 are about 50% and 10% larger than those of LaRu 2 Si 2 and LaRu 2 Ge 2 , respectively.

Fermi surfaces of YbGa2

Abstract We have observed the de Haas-van Alphen oscillation of YbGa 2 . It is a semimetal and Fermi surfaces consist of closed electron and hole surfaces.