Solid State Phenomena Vol. 215

Abstract: A simple method for obtaining ZnO-Fe₃O₄ nanocomposites using solid-state reaction Zn + 3Fe₂O₃ ZnO + 2Fe₃O₄ is suggested. An analysis of the characteristics and properties of ZnO-Fe₃O₄ nanocomposites was carried out by a combination of structural and physical methods (X-ray diffraction, scanning electron microscopy, photoelectron spectroscopy, Mössbauer measurements, X-ray fluorescent analysis, and magnetic measurements). The magnetization of the hybrid ZnO-Fe₃O₄ films is equal to 440 emu/cm³. The resulting Fe₃O₄ nanoparticles are surrounded by a ZnO shell and have sizes ranging between 20 and 40 nm.

Abstract: Influence the deposition of La³⁺ ions by monovalent K⁺ ions on magnetorefractive effect on magnetoreflaction and magnetotransmission modes in the infrared range for La_1-xK_xMnO₃ epitaxial thin-films (х=0.05, 0.10, 0.15 и 0.18) has been studied. It has been shown that the magnetorefractive effect, transversal Kerr effect and magnetoresistance reach the maximum in optimally doped films at highest Curie temperature. The good agreement between calculated in framework of magnetorefractive effect theory and experimental data takes place only for optimally doped films, with potassium concentrations of 15 % and 18 %. At the other doping levels the films become charge and magnetic inhomogeneous. Magnetic and charge homogeneity influence strongly on magnetooptical effects in films. The resonance-like lines in magnetoreflection spectra of films are connected with the shifting of reflection minimum before the phonon bands under a magnetic field has been observed.

Abstract: Solid-state reactions between Ge and Mn films are systematically examined using X-ray diffraction, photoelectron spectroscopy and magnetic measurements. The films have a nominal atomic ratio Ge:Mn = 40:60 and are investigated at temperatures from 50 to 500 °С. It is established that after annealing at ~120 °С, the ferromagnetic Mn₅Ge₃ phase is the first phase to form at the 40Ge/60Mn interface. Increasing the annealing temperature to 500 °С leads to the formation of the ferromagnetic phase with a Curie temperature T_C ~ 360 K and magnetization M_S ~ 140-200 emu/cc at room temperature. Analysis of X-ray diffraction patterns and the photoelectron spectra suggests that the increased Curie temperature and magnetization are related to the migration of C and O atoms into the Mn₅Ge₃ lattice and the formation of the Nowotny phase Mn₅Ge₃С_xO_y. The initiation temperature (~120 °С) of the Mn₅Ge₃ phase is the same both for solid-state reactions in Ge/Mn films, as well as for phase separation in Ge_xMn_1-x diluted semiconductors. We conclude that the synthesis of the Mn₅Ge₃ phase is the moving force for the spinodal decomposition of the Ge_xMn_1-x diluted semiconductors.

Abstract: Structural, magnetic and magneto-optical properties of borate glasses co-doped with Fe and the lager radius ions are presented. Maghemite, γ-Fe₂O₃, nanoparticles arise in the glasses as a result of their thermal treatment in different regimes. Magnetization FC and ZFC temperature dependences demonstrate the superparamagnetic behavior of the particles with the blocking temperature below the room temperature. The EMR spectra measurements revealed a significant anisotropy with a large contribution of the nanoparticles’ surface anisotropy. The FR maximum centered near 700 nm is a characteristic feature of the investigated glasses.

Abstract: In this paper the analysis of structure changes in series of amorphous alloys with different Fe/Ni and Fe/Co ratio and Cr addition is made. It has been shown that within temperature range 23⁰С <T< 450⁰С the structure of alloys keeps its amorphous character and only a slight changes in heat flow occur. At temperatures above 450°C the structure evolution depends of the Fe/Ni and Fe/Co ratio and some dopants.

Abstract: The subject of this study is the change of the electrical resistivity of Fe-based metallic glasses during heat treatment. Electrical resistivity is a structure-sensitive characteristic of materials. In metallic glasses, the scattering of conduction electrons on the disordered structure is the main mechanism responsible for the electrical resistivity. Hence amorphous metallic alloys have a much higher residual resistivity as compared to their crystalline analogs. It is typical for metallic glasses that the temperature coefficient of resistivity (TRC) is smaller than for the corresponding crystalline materials, and it can be either positive or negative.

Abstract: We have studied the scaling evolution of the structure and magnetic properties of the melt-spun Fe₇₀Cr₁₅B₁₅(Sn) alloys. The magnetic percolation cluster about the percolation threshold forms at the vitrification stage that is determined by both the kinetics of magnetic and of transport properties and the variation of fractal dimensionality. Alloying by tin of contact surface of ribbon decreases the temperature of the cluster formation. It is shown that the evolution of a fractal ordering affects the kinetics of the physical properties of the alloys. The spectra of fractal dimensionality identify the symmetry character of melt-spun alloys. Fractal dimension D_f is reduced at the increasing complexity of hierarchical system.

Abstract: Magnetic properties, thermal stability and structure of the alloys - (Fe_0.6Co_0.4)₈₆Hf₇B₆Cu₁ (1), (Fe_0.7Co_0.3)₈₈Hf₇B₄Cu₁ (2) and (Fe_0.7Co_0.3)₈₈Hf₄Mo₂Zr₁B₄Cu₁ (3) obtained in the form of ribbons quenched from the melt were investigated after their nanocrystallization in the course of the thermal (TA) and stress (SA) annealings in the air at different temperatures. In all three alloys SA resulted in the induction of magnetic anisotropy with an easy axis along the direction of the ribbon. It is established that the alloy 3 after SA at 620°C for 20 min has the best thermal stability of magnetic properties, which remained practically unchanged after the subsequent annealing at 550°C for 26 hours. Magnetic properties of the alloys 1 and 2 subjected to SA under the same conditions did not change after annealing at 500°C.

Abstract: In this paper we research the process of magnetization of iron-containing coatings obtained on aluminum and titanium plasma electrolytic oxidation. It is shown that the formation of a remnant magnetic moment mainly determined by the magnetostatic interaction particles (phases). This interaction leads to a decrease of the blocking volume of particles (phases). Thus, a large number of superparamagnetic particles (phases) obtain stable magnetic moments and are involved in creating of the remnant magnetization of the sample.

Abstract: In this study the features of the growth processes of copper silicide nanostructures on Si (111) were investigated. The nanostructures were grown by molecular beam epitaxy. It has been shown that the islands and nanowires are formed at the substrate temperature 550°C. The nanostructures have ideal facets and lateral edges. The long side of nanowires is oriented along the crystallographic direction <110> Si. We have shown that there is a range of thicknesses at which nanowires generally grow.