Haruhisa Ikezawa

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.

Fermi surface properties of ferromagnetic CeRu2Ge2

Abstract We have performed a dHvA effect study on the ferromagnetic heavy fermion compound CeRu2Ge2. Six spin-split dHvA frequency branches are observed in the (1 0 0) and (1 1 0) planes. The angular dependence of the dHvA frequencies is mostly consistent with the result reported by King and Lonzarich (KL), except that we have successfully observed the dHvA signal from a large hole surface for fields parallel to [0 0 1] and a new low-frequency branch. The effective masses measured for fields in the (0 0 1) plane agree with those of KL and do not depend on field strength. On the other hand, those for fields parallel to [0 0 1] differ considerably from those of KL and are found to decrease with increasing field. Moreover, the measured effective mass of the large hole surface is less than half of the value expected from the electronic specific heat coefficient.

Change of the Fermi surfaces at the magnetic transition in NdIn3

Abstract We have done de Haas-van Alphen experiments for NdIn3 in high fields up to 17 T. The drastic change of the Fermi surfaces at the metamagnetic transition is presented.

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.

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.