Solid State Phenomena Vol. 215

Abstract: HoAl_3-xGa_x(BO₃)₄ (0 ≤ х ≤ 3) single crystals were grown from Bi₂Mo₃O₁₂Li₂MoO₄-based fluxes. Structural inversion twinning depending on crystal composition and heat treatment conditions is revealed. It is established that upon substitution of Ga³⁺ ions for Al³⁺ the magnetic characteristics of the crystals do not significantly change, while the magnetoelectric polarization decreases with increasing gallium content. The measured value and sign of polarization charges depend on a ratio between the left and right isomers.

Abstract: We present the results of investigations of the spin-polarized current and spin dynamics in the hybrid structures ferrimagnetic insulator/ferromagnetic metal subjected to microwave radiation. We studied the La_0.7Sr_0.3MnO₃/Y₃Fe₅O₁₂ bilayer films on the Gd₃Ga₅O₁₂ substrate. It was experimentally established that under the action of spin pumping the resistance of the La_0.7Sr_0.3MnO₃ film changes. The value of ΔR is maximum in the sample with a La_0.7Sr_0.3MnO₃ layer thickness of 10 nm and sharply drops as the manganite film thickness is increased. The resistance decreases in the paramagnetic region and grows in the ferromagnetic region at temperatures below the metal-insulator transition point. The variation in the resistance of the manganite film can be attributed to the correlation of the spin dynamics and transport properties of conduction electrons in the structure.

Abstract: PbFeBO₄ and PbMnBO₄ single crystals were synthesized. The X-ray, magnetic, dielectric, Mössbauer, and resonance investigations of the crystals were fulfilled. It is established that single-crystal PbFeBO₄ is an antiferromagnet with a Néel temperature T_N =114 K, while PbMnBO₄ is a ferromagnet with a Curie temperature T_C = 31 K. Both single-crystal compounds have a strong anisotropy of the magnetic and dielectric properties.

Abstract: Multiferroics based on BiFeO₃ with spatially-modulated antiferromagnetic structure are investigated. The goal of this work is to define possibility of orientation phase transitions in magnetic and electric system by replacing Bi with 4f Nd ion depending on temperature in external magnetic field. On Nd_xBi_1-xFeO₃ films the measurements of permittivity, loss tangent at frequences 100 Hz < ω < 10⁵ Hz and at temperatures 300 К < T < 1000 K without magnetic field and in magnetic field with H=0.8 Т were made. A drop in temperature dependence of permittivity in magnetic field was found. Magnetoelectric properties can be explained in model of changing of magnetic structure in magnetic field as a result of interaction of electric and magnetic subsystems.

Abstract: Effects of both the phase and the amplitude inhomogeneities of different dimensionalities on the Greens function and on the one-dimensional density of states of spin waves in the sinusoidal superlattice have been studied. Processes of multiple scattering of waves from inhomogeneities have been taken into account in the self-consistent approximation.

Abstract: Brillouin light spectroscopy method of magnetic materials was used for experimental study of multimode propagation characteristics of surface magnetostatic waves in an irregular ferrite waveguide. It was experimentally demonstrated that the spatial transformation of modes is possible in tapered ferrite planar waveguide due to breaking of the axis symmetry.

Abstract: A model describing the propagation of surface magnetostatic waves in the one-dimensional finite length magnonic crystal (MC) with losses was constructed. The features of microwave pulse passing through the band gap of MC were investigated experimentally. The conditions of soliton-like pulse formation were defined experimentally and by numerical simulation.

Abstract: We report on a sensitive spectroscopic technique for probing the spin excitations of individual submicron magnets. This technique uses a high mobility two dimensional electron gas (2DEG) confined in a GaAs/AlGaAs heterojunction to pick up the oscillating dipolar magnetic field emanating from the individual spin wave modes of micromagnets fabricated at its surface. We review a range of dynamic phenomena that demonstrate the formation of magnetostatic waves in finger gate arrays, dipolar edge spin waves in bar magnets, vortex hysteresis in magnetic dots and the photovoltage dependence on microwave polarization.

Abstract: The domain structure dependence on the uniaxial anisotropy constant has been considered in a micrometer-thick film by means of the two-dimensional micromagnetic simulation. The film has both uniaxial and tetra-axial magnetic anisotropies. The new type domain structures and walls caused by the tetra-axial anisotropy presence are predicted.

Abstract: Lorentz electron microscopy was used to compare the domain structure in Mn_55.5А1_45.5 C_0.5 ferromagnetic alloy in different structural states. The samples with different structural states were processed by means of deformation and thermal treatment at different conditions. It was established, that grain refinement causes the changes in domain structure configuration and affects the magnetization mechanism.