Main Fermi Surface Research Articles

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.

De Haas-van Alphen Effect and Fermi Surface of the Antiferromagnetic Compound NdPb3

We have observed the de Haas-van Alphen oscillation of the antiferromagnetic compound NdPb 3 . Main Fermi surfaces consist of four closed ones, which are in good agreement with the results of band calculations based on the FLAPW method for the non-magnetic reference compound LuPb 3 . The cyclotron effective masses are in the range of 0.4 m 0 to 3 m 0 .

Local-density approach to the Fermi surfaces of CeRu 2Si 2 and LaRu 2Si 2

In the itenerant 4f electron model, electronic structures are calculated for CeRu 2Si 2 and LaRu 2Si 2 by a relativistic APW method. The main Fermi surface is a large hole sheet in LaRu 2Si 2 and a hole and an electron sheet in CeRu 2Si 2. Evidence for these sheets is available from published results of de Haas-van Alphen experiments.

A Local-Density Band Theory for the Fermi Surface of the Heavy-Electron Compound CeRu2Si2

On the basis of the itinerant-electron model for the 4f electrons, the energy band structure and the Fermi surface are calculated for the metamagnetic heavy-electron compound CeRu 2 Si 2 having the low-temperature electronic specific heat coefficient γ of 350 mJ/K 2 mol. by a self-consistent symmetrized relativistic APW method with the exchange and correlation potential in a local-density approximation. The main Fermi surface consists of a large closed hole sheet and a complicated electron sheet like a jungle gym. The Fermi surface topology is consistent with the experimental result for the high-field magneto-resistance. By comparison with the electronic structure of LaRu 2 Si 2 , effects of the 4f bands on the Bloch states on the Fermi surface in CeRu 2 Si 2 are investigated in detail. Strong evidences for existence of the electron sheet are found in available experimental de Haas-van Alphen frequencies. The enhancement factor for γ is estimated as 38.

Electronic Structure and Fermi Surface of LaRu2Si2

The energy band structure and the Fermi surface are calculated for LaRu 2 Si 2 with a body-centered tetragonal crystal structure by a self-consistent relativistic symmetrized APW method with the exchange and correlation potential in the local-density approximation. The main Fermi surface is an extraordinarily large, closed hole sheet with a cross-sectional area exceeding the size of the Brillouin zone itself. There are additionally small hole and electron sheets, all of which have no open orbit. The Fermi surface topology is consistent with the experimental result for the high-field transverse magnetoresistance. By these Fermi surfaces, both the magnitude and the angular dependence of the frequency branches of the de Haas-van Alphen effect measured recently by Ōnuki et al. can be explained reasonably well. The Fermi surfaces of the related heavy-electron compound CeRu 2 Si 2 and ferromagnetic compound CeRu 2 Ge 2 are discussed briefly.

Magnetoresistance and de Haas-van Alphen Effect in CeRu2Si2and LaRu2Si2

We have measured the magnetoresistance and de Haas-van Alphen (dHvA) effect in CeRu 2 Si 2 and LaRu 2 Si 2 . From the results of magnetoresistance, CeRu 2 Si 2 is concluded to be a compensated metal, possibly possessing an open orbit along the c -axis of the tetragonal structure. On the other hand, LaRu 2 Si 2 is an uncompensated metal, showing the saturated magnetoresistance. These results imply that the 4 f electrons in CeRu 2 Si 2 are itinerant. In the dHvA experiments of LaRu 2 Si 2 , we have found a large ellipsoidal Fermi surface which occupies roughly half of the Brillouin zone in volume. On the other hand, CeRu 2 Si 2 possesses multiply connected Fermi surfaces in part, although main Fermi surfaces are not observed yet.

Effect of the Spin-Orbit Interaction on the Fermi Surface of LaSn3

Electronic structure is calculated for LaSn 3 by a self-consistent relativistic APW method with the one-electron potential in the local-density approximation. LaSn 3 is a reference for the mixed-valence compound CeSn 3 in which the 4f electrons have recently been proven to be itinerant and contribute directly to the formation of the Fermi surface. Here, the relation between the Fermi surfaces of LaSn 3 and CeSn 3 is investigated. The main Fermi surface of LaSn 3 consists of a distorted hole sphere and a network with slender arms, both of which are connected with small necks. These sheets can explain the de Haas-van Alphen effect and the high-field magnetoresistance reasonably well. The distorted hole sphere in LaSn 3 and the hole sheet in CeSn 3 originate from the eighth band, and look similar to each other. In CeSn 3 , the electron sheet exists as a result of compensation.

Interpretation of Positron Annihilation Curves for Lithium by Mijnarends' Method. Has the Fermi Surface of Lithium a Neck?

AbstractThe positron annihilation curves of Donaghy and Stewart for lithium have been reinterpreted using Mijnarends' method. In this way it has been possible to split the total number of counts into two parts, one corresponding to electron momenta inside the main Fermi surface, the other arising from higher momentum components of the conduction electron wave functions and core annihilation. Evidence is found for the possible existence of a neck in the Fermi surface in the (110) direction with a radius of the order of 13% of the free electron sphere radius. The need for more detailed experimental investigations of positron annihilation in lithium is emphasized.