Prediction for new magnetoelectric fluorides

We use symmetry considerations in order to predict new magnetoelectric fluorides. In addition to these magnetoelectric properties, we discuss among these fluorides the ones susceptible to present multiferroic properties. We emphasize that several materials present ferromagnetic properties. This ferromagnetism should enhance the interplay between magnetic and dielectric properties in these materials.Comment: 12 pages, 4 figures, To appear in Journal of Physics: Condensed Matte

Dislocation sinks efficiency for self-point defects in iron and vanadium crystals

The effect of the dislocations stress fields on their sink efficiency for self-point defects (interstitial atoms and vacancies) is studied in the temperature range of 293–1000 K and at the dislocation density values of 1 × 1012–3 × 1014 m−2 in body-centered cubic (BCC) iron and vanadium crystals. Straight screw and edge dislocations in 〈111〉{110}, 〈111〉{112}, 〈100〉{100}, and 〈100〉{110} slip systems are considered. Defect diffusion is simulated via the object kinetic Monte Carlo method. The energies of the interaction of defects with dislocations are calculated within the anisotropic linear theory of elasticity. The dislocation sink efficiency is analytically represented as a function of temperature and dislocation density

Effect of external stresses on efficiency of dislocation sinks in BCC (Fe, V) and FCC (Cu) crystals

The efficiency of linear sinks for selfpoint defects (SPDs) elastically interacting (dislocations) and not interacting with sinks with the density of 3 × 1014 m–2 is calculated for BCC (Fe, V) and FCC (Cu) crystals at the temperature 293 K using the object kinetic Monte Carlo technique, depending on type and value of applied mechanical load (up to 200 MPa) and types of linear sinks. Full straight dislocations in slip systems [111](1 0), [111](11 ), [100](001), and [100](011) for Fe and V and [100](001) for Cu are considered for dislocation sinks (DSs). Orientations of noninteracting linear sinks (NILSs) coincide with those of DSs. Interaction of SPDs with internal (dislocation) and external stress fields is calculated within the framework of anisotropic linear theory of elasticity. Relative changes in efficiency of different codirectional linear sinks (either interacting or not interacting with SPDs) under action of applied stress are approximately identical under low stress. Radiation creep rates are calculated for the considered crystals under uniaxial stress in the stationary regime of Frenkel pairs generation. The creep rate strongly depends on the loading direction and Burgers vector of dislocations in Fe and V, and it is almost independent of these parameters in Cu. At the same generation rate of Frenkel pairs, the radiation creep rate averaged over all loading directions is significantly higher in BCC (Fe, V) crystals containing dislocations with the Burgers vector a/2〈111〉 than in FCC (Cu) crystals

Spin wave resonances in antiferromagnets

Spin wave resonances with enormously large wave numbers corresponding to wave vectors 10^5-10^6 cm^{-1} are observed in thin plates of FeBO3. The study of spin wave resonances allows one to obtain information about the spin wave spectrum. The temperature dependence of a non-uniform exchange constant is determined for FeBO3. Considerable softening of the magnon spectrum resulting from the interaction of magnons, is observed at temperatures above 1/3 of the Neel temperature. The excitation level of spin wave resonances is found to depend significantly on the inhomogeneous elastic distortions artificially created in the sample. A theoretical model to describe the observed effects is proposed.Comment: 6 pages, 6 figure

Phase-space structures in quantum-plasma wave turbulence

The quasilinear theory of the Wigner-Poisson system in one spatial dimension is examined. Conservation laws and properties of the stationary solutions are determined. Quantum effects are shown to manifest themselves in transient periodic oscillations of the averaged Wigner function in velocity space. The quantum quasilinear theory is checked against numerical simulations of the bump-on-tail and the two-stream instabilities. The predicted wavelength of the oscillations in velocity space agrees well with the numerical results