Fermion theories on a 2d torus with Wilson action improved by Pauli -- Villars regularization

Vectorial and anomaly free chiral U(1) fermion models on a 2d finite lattice are considered. It is demonstrated both numerically and analytically that introduction of Pauli -- Villars type regularization supresses the symmetry breaking effects caused by the Wilson term.Comment: 17 pages, Latex, 6 eps-figure

Simulation of three-dimensional micromagnetic structures in magnetically uniaxial films with in-plane anisotropy: Static structures

The possible types of transition structures that can arise between the regions of vortex asymmetric domain walls that exist in magnetically uniaxial permalloy films with in-plane anisotropy have been studied by the method of three-dimensional computer simulation of the magnetization behavior. It has been established that, along with the previously found structures of vertical Bloch lines (VBLs), other types of structures can exist, namely, singular (Bloch) points and clusters that consist of VBLs and Bloch points. Spatial configurations and topological characteristics of transition structures have been calculated numerically. © 2013 Pleiades Publishing, Ltd

Transition micromagnetic structures in asymmetric vortexlike domain walls (Static solutions and dynamic reconstructions)

The possible types of transition structures with a three-dimensional magnetization distribution over regions in the vortex asymmetric domain walls that exist in magnetically uniaxial soft magnetic films with in-plane anisotropy are studied by computer simulation in terms of a micromagnetic approach. It is shown that the possible structure types include both the type of vertical Bloch lines that was discussed earlier in other works and new types, namely, singular (Bloch) points and clusters consisting of vertical Bloch lines and Bloch points. The spatial configurations of the transition structures are calculated and their topological properties are found. The numerical simulation of the dynamics of closely spaced substructure regions reveals various scenarios of their interaction, including annihilation accompanied by energy release and the excitation of nonlinear waves. © 2013 Pleiades Publishing, Ltd

Simulation of three-dimensional micromagnetic structures in magnetically uniaxial films with in-plane anisotropy. Dynamics and structural reconstructions

Transition processes in nonequilibrium micromagnetic structures that represent regions of various types of asymmetrical vortex domain walls with closely spaced transition structural elements, including vertical Bloch lines (VBLs), singular points, and clusters consisting of VBLs and singular points, have been studied by the method of three-dimensional numerical simulation of the magnetization behavior. The realization of various scenarios of dynamic behavior, including the annihilation of transition elements accompanied by the liberation of energy and the initiation of wave processes, has been shown to be possible. The simulation was performed for the case of magnetically uniaxial ferromagnetic films with an easy axis parallel to their surface with exact allowance for the inhomogeneous exchange, magnetoanisotropic, and magnetostatic interactions. © 2013 Pleiades Publishing, Ltd

Two-dimensional micromagnetic simulation of domain structures in films with combined anisotropy

The transformation of the domain structure of micrometer-thick films with variations in the induced uniaxial anisotropy constant with the easy magnetization axis perpendicular to the film surface has been investigated using numerical micromagnetic simulation in the framework of a two-dimensional model of the magnetization distribution. The case where the tetra-axial crystallographic anisotropy exists in the film with uniaxial magnetic anisotropy has been considered. The transformation of the open domain structure into the structure with a magnetic flux closed inside the sample has been investigated in detail, and new types of 109-degree and 90-degree vortex-like domain walls and periodic domain structures have been obtained. © 2013 Pleiades Publishing, Ltd

Transport properties and the anisotropy of Ba_{1-x}K_xFe_2As_2 single crystals in normal and superconducting states

The transport and superconducting properties of Ba_{1-x}K_xFe_2As_2 single crystals with T_c = 31 K were studied. Both in-plane and out-of plane resistivity was measured by modified Montgomery method. The in-plane resistivity for all studied samples, obtained in the course of the same synthesis, is almost the same, unlike to the out-of plane resistivity, which differ considerably. We have found that the resistivity anisotropy \gamma=\rho_c /\rho_{ab} is almost temperature independent and lies in the range 10-30 for different samples. This, probably, indicates on the extrinsic nature of high out-of-plane resistivity, which may appear due to the presence of the flat defects along Fe-As layers in the samples. This statement is supported by comparatively small effective mass anisotropy, obtained from the upper critical field measurements, and from the observation of the so-called "Friedel transition", which indicates on the existence of some disorder in the samples in c-direction.Comment: 5 pages, 5 figure