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.-

Transport properties of nanosystems with conventional and unconventional charge density waves

We report a systematic study of transport properties of nanosytems with charge density waves. We demonstrate, how the presence of density waves modifies the current-voltage characteristics. On the other hand hand, we show that the density waves themselves are strongly affected by the applied voltage. This self-consistent problem is solved within the formalism of the nonequilibrium Green functions. The conventional charge density waves occur only for specific, periodically distributed ranges of the voltage. Apart from the low voltage regime, they are incommensurate and the corresponding wave vectors decrease discontinuously when the voltage increases.Comment: 7 pages, 7 figures, revte

First pterosaur remains from the Cretaceous of Poland

The first records of pterosaurs from the Cretaceous of Poland are reported, on the basis of fragmentary remains from the marine Upper Albian (Lower Cretaceous) of the Annopol Anticline, central Poland. The new material consists of four bone fragments, tentatively interpreted as: 1) a portion of wing phalanx; 2) a medial element of fused skull bones (parietal crest?); 3) a fragmentary carpal or tarsal; and 4) a distal phalanx of the pes (or a very small fragment of a long cervical vertebra). Previously, only the remains of marine vertebrates have been reported from the Cretaceous of the Annopol area. The pterosaur fossils studied most probably belonged to individuals that died while over the sea. The possibility that they represent remains dropped from floating carcasses, introduced into the marine environment by rivers, is regarded as less probable, as there are no remains of dinosaurs or other terrestrial fauna in the Annopol deposits

Properties of an almost localized Fermi liquid in applied magnetic field revisited: Statistically consistent Gutzwiller approach

We discuss the Hubbard model in an applied magnetic field and analyze the properties of neutral spin-1/2 fermions within the so-called statistically consistent Gutzwiller approximation (SGA). The magnetization curve reproduces in a semiquantitative manner the experimental data for liquid 3 He in the regime of moderate correlations and in the presence of small number of vacant cells, modeled by a non-half filled-band situation, when a small number of vacancies (up to 5%) is introduced in the virtual fcc lattice. We also present the results for the magnetic susceptibility and the specific heat, in which a metamagnetic-like behavior is also singled out in a non-half-filled band case