Ferromagnetism in UGe2 : A microscopic model

Anderson lattice model is used to rationalize the principal features of the heavy fermion compound UGe2 by means of the generalized Gutzwiller approach (the SGA method). This microscopic approach successfully reproduces magnetic and electronic properties of this material, in a qualitative agreement with experimental findings from the magnetization measurements, the neutron scattering, and the de Haas-van Alphen oscillations. Most importantly, it explains the appearance, sequence, character, and evolution in an applied magnetic field of the observed in UGe2 ferro- and, para-magnetic phases as an effect of a competition between the f-f electrons Coulomb interaction energy and f-conduction electrons kinetic energy (hybridization)Comment: submitted to Phys. Rev.

Criticalities in the itinerant ferromagnet UGe2_{2}

We provide a microscopic description of the magnetic properties of UGe$_2$ and in particular, of its both classical and quantum critical behavior. Namely, we account for all the critical points: the critical ending point (CEP) at the metamagnetic phase transition, the tricritical point, and the quantum critical end point at the ferromagnetic to paramagnetic phase transition. Their position agrees quantitatively with experiment. Additionally, we predict that the metamagnetic CEP can be traced down to zero temperature and becomes quantum critical point by a small decrease of both the total electron concentration and the external pressure. The system properties are then determined by the quantum critical fluctuations appearing near the instability point of the Fermi surface topology.Comment: 4 pages, 4 figures, PACS number: 71.27.+a, 75.30.Kz, 71.10.-

Model of hard spheroplatelets near a hard wall

A system of hard spheroplatelets near an impenetrable wall is studied in the low-density Onsager approximation. Spheroplatelets have optimal shape between rods and plates, and the direct transition from the isotropic to biaxial nematic phase is present. A simple local approximation for the one-particle distribution function is used. Analytical results for the surface tension and the entropy contributions are derived. The density and the order-parameter profiles near the wall are calculated. The preferred orientation of the short molecule axes is perpendicular to the wall. Biaxiality close to the wall can appear only if the phase is biaxial in the bulk.Comment: 11 pages, 9 figures, revised version published in PR