R. Settai

Fermi surface of the heavy-fermion superconductorPrOs4Sb12

We have investigated the de Haas-van Alphen effect in the Pr-based heavy-fermion superconductor PrOs 4 Sb 1 2 . The topology of Fermi surface is close to the reference compound LaOs 4 Sb 1 2 and well explained by the band-structure calculation based on the FLAPW (full potential linearized augmented-plane-wave)-LDA (local-density approximation) +U method, where the 4f electrons are localized. We have confirmed a highly enhanced cyclotron effective mass (2.4-7.6)m 0 , which is apparently large compared to the usual Pr-based compounds.

De Haas-van Alphen effect study of CeRu2Si2

Abstract We report an extensive study of the angular dependence of the de Haas-van Alphen frequencies for the field directions in the (0 1 0) and (0 0 1) planes, and the field dependence of the effective masses and frequencies below and above the metamagnetic transition field (Hm) in CeRu2Si2. The present study confirms our previous conclusion that the Fermi surfaces change from those of itinerant f electrons below Hm to those of localized f electons above Hm.

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 .

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.

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.

Single crystal growth and superconducting properties of CeRu2

Abstract We have grown a single crystal of the superconductor CeRu2 by a zone-melting method in an induction furnace. We have measured the lower and upper superconducting critical fields, which are estimated as 250–400 Oe and 74 kOe at 0 K, respectively. Hc2 is slightly anisotropic, 64.8 kOe for the field along the 〈1 0 0〉 direction and 65.6 kOe for 〈1 1 0〉 at 1.5 K. The anomaly in the magnetization below Hc2 reported by another group was also investigated.

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 .

The specific heat of single crystal NdCu2

Abstract We present the measurements of the specific heat C of NdCu 2 on single crystal samples of high purity in the temperature range between 0.7 K and 70 K. We observed three peaks: two are first order peaks at T R1 = 3.97 K and T R2 = 4.22 K and one is the antiferromagnetic transition at T N = 6.50 K. The gap in the density of state of the antiferromagnetic spin wave band is found below T R2 . The specific heat observed below T R1 is well expressed by the gap type formula C = γT + β m T 3 exp(− δ / κ B T ). We show good correlation between the entropies of NdCu 2 and the magnetic resistivity measured along the crystal b -axis.

Anisotropic magnetic and transport properties of NdCu2

Abstract We have measured the magnetization, magnetic susceptibility, magnetoresistance, Hall effect and magnetocaloric effect on a NdCu2 single crystal. The anisotropy of the magnetic properties is explained by the crystal field effect. For the field along the b-axis, three metamagnetic transitions were clearly observed in the magnetization, magnetocaloric effect and transport properties. The origin of these anomalies in the transport properties at the metamagnetic transitions is discussed in terms of the magnetocaloric effect.