[en] Published in summary form only

[en] We analyze a model of a one-dimensional electron-gas interacting with an antiferromagnetic Heisenberg spin-1/2 chain via the spin-exchange interactions. Using a solution at a special limit, we characterize the gapless modes of the spin-gap fixed point at weak coupling J_K<< J_H,E_F. We show that the only gapless pairing mode with divergent susceptibility is a composite odd-parity/odd-frequency singlet-pairing order parameter, while the ordinary BCS even-parity singlet-pairing mode is incoherent. For two-leg ladder systems, we note that it is possible to have a range of doping where the chemical potential cuts only the antibonding band while the bonding band remains half filled. We propose that in such a state the two-leg ladder is effectively realizing the one-dimensional Kondo-Heisenberg model

No abstract available

[en] Possible exchange mechanisms between sites with two electrons in three orbitals subject to strong Hund's rule correlations are studied. While three itinerant orbitals lead to antiferromagnetism, one localized and two itinerant orbitals give rise to ferromagnetism. The results are discussed in the context of the half-metallic ferromagnet CrO₂

[en] Full text: Narrow-band semimagnetic semiconductors (SMS) Pb1-xMnxTe are unique materials for infrared (IR) optoelectronics.The investigation of Faraday effect in Pb1-xMnxTe thin films of SMS is of a special interest. So it can be used at the construction of optic isolators, amplifiers, IR detectors and other equipments.In the given work Pb1-xMnxTe thin films (SMS) have been produced, the interband Faraday effect in these semiconductors has been theoretically and experimentally studied. Opportunities of making IR detectors have been studied. Pb1-xMnxTe (x=0.005 0.06) thin films have been grown at BaF2 substrates by the method of molecular beam condensation. The optimal conditions of producing thin films with high crystallic perfection, electrophysical and optical parameters have been determined [1]. The energy spectrum and wave functions have been theoretically calculated for quantum-sized films of Pb1-xMnxTe SMS in the case when the surface of the film is perpendicular to the axis X and the spin-spin exchange interaction occurs between the electrons in the conductivity band (valence band) and the electrons of half-filled d-shells of manganese ions as well as taking into account electron spins and the band nonparabolicity. For the calculation of the spectra and wave functions double-band Kane model has been used. On the basis of the found formulae an analytical equation has been found out for interband Faraday rotation (IFR) depending on the energy of the incident photon, band gap and the film thickness. It has been shown that by the decrease in the band gap the value of the IFR angle increases too [2]. The formula of parabolic approximation has been also obtained. The dependence of IFR angle on photon energy, band gap and the film thickness has been built. It has been specified that the decrease of the film thickness leads to a strong increase of IFR angle. The contribution of nonparabolicity into IFR angle has been established, so taking into consideration the band nonparabolicity results in the increase of IFR angle. In a nongap state a substantial increase occurs in IFR angle. The obtained results are in a good conformity with the experimental data. In this work the dependence of IFR angle on photon energy, band gap and the film thickness are given. It has been specified that the decrease of the film thickness leads to a strong increase of IFR angle.

No abstract available

[en] Various approaches are discussed for producing polarized nuclear targets for high energy physics experiments. As a unifying theme, examples are drawn from experiments to measure spin dependent structure functions of nucleons in deep inelastic scattering. This single physics goal has, over roughly two decades, been a driving force in advances in target technology. Actual or planned approaches have included solid targets polarized by dynamic nuclear polarization (DNP), several types of internal targets for use in storage rings, and gaseous ³He targets polarized by spin-exchange optical pumping. This last approach is the type of target adopted for SLAC E-142, an experiment to measure the spin structure function of the neutron, and is described in detail

No abstract available

[en] This contribution addresses the question of whether or not the ground state of a frustrated spin-1/2 Heisenberg model can be smoothly related to the ground state of a simple tight-binding model at half-filling in an appropriately chosen magnetic field. This continuity is considered explicitly for an eight-site square-lattice Hubbard model with nearest- and next-nearest-neighbor hopping, which approaches a frustrated Heisenberg model with nearest- and next-nearest-neighbor antiferromagnetic exchange coupling in the limit of large Hubbard U. In addition, a counterexample to the widely held belief that the half-filled band of the ordinary Hubbard model is nonmagnetic has been found in the regime where the hopping parameters and Hubbard interaction are all the same order of magnitude

[en] Cooper pairing of electrons in a crystal with regularly distributed localized spins is considered. The case is studied in which exchange interaction between the electrons and localized spins leads to helical magnetic ordering of the localized spins in the superconducting state, whereas in the absence of superconductivity ferromagnetic order would occur. It is shown that scattering of conducting electrons by nonmagnetic impurities narrows the region of existence of the superconducting phase with spin ordering (HS phase). The narrowing, however, is not very pronounced even in dirty crystals. Thus the requirement of the purity of the crystals in which the HS phase may be observed is not very rigid