Magnetic anisotropy in strained manganite films and bicrystal junctions

Transport and magnetic properties of LSMO manganite thin films and bicrystal junctions were investigated. Manganite films were epitaxially grown on STO, LAO, NGO and LSAT substrates and their magnetic anisotropy were determined by two techniques of magnetic resonance spectroscopy. Compare with cubic substrates a small (about 0.3 persentage), the anisotropy of the orthorhombic NGO substrate leads to a uniaxial anisotropy of the magnetic properties of the films in the plane of the substrate. Samples with different tilt of crystallographic basal planes of manganite as well as bicrystal junctions with rotation of the crystallographic axes (RB - junction) and with tilting of basal planes (TB - junction) were investigated. It was found that on vicinal NGO substrates the value of magnetic anisotropy could be varied by changing the substrate inclination angle from 0 to 25 degrees. Measurement of magnetic anisotropy of manganite bicrystal junction demonstrated the presence of two ferromagnetically ordered spin subsystems for both types of bicrystal boundaries RB and TB. The magnitude of the magnetoresistance for TB - junctions increased with decreasing temperature and with the misorientation angle even misorientation of easy axes in the parts of junction does not change. Analysis of the voltage dependencies of bicrystal junction conductivity show that the low value of the magnetoresistance for the LSMO bicrystal junctions can be caused by two scattering mechanisms with the spin- flip of spin - polarized carriers due to the strong electron - electron interactions in a disordered layer at the bicrystal boundary at low temperatures and the spin-flip by anti ferromagnetic magnons at high temperatures.Comment: 26 pages, 10 figure

Structure and propertties of ball milled utrahigh-molecular weight Polyethylene - clay composite

In this work the composite material based on polymer matrix filled with clay is studied. The preparation of powder composition consists of mechanical activation of substances and further common ball milling of polymer and clay in a high energy planetary ball mill. The process is divided into two stages; the first stage involves crushing of clay to obtain a nanosized powder, and in the second stage preparation of powdered nanocomposite is carried out. New clay-polymer composite shows considerable increase in modulus of elasticity and a decrease in coefficient of friction

Spin-dependent electron transport in manganite bicrystal junctions

Magnetic bicrystal films and junctions of magnetic La0.67Sr0.33MnO3 (LSMO) and La0.67Ca0.33MnO3 (LCMO) films epitaxially grown on NdGaO3 substrates with the (110) planes of their two parts misoriented (tilted) at angles of 12A degrees, 22A degrees, 28A degrees, and 38A degrees are investigated. For comparison, bicrystal boundaries with a 90A degrees misorientation of the axes of the NdGaO3 (110) planes were fabricated. The directions of the axes and the magnetic anisotropy constants of the films on both sides of the boundary are determined by two independent techniques of magnetic resonance spectroscopy. The magnetic misorientation of the axes in the substrate plane has been found to be much smaller than the crystallographic misorientation for tilted bicrystal boundaries, while the crystallographic and magnetic misorientation angles coincide for boundaries with rotation of the axes. An increase in the magnetoresistance and characteristic resistance of bicrystal junctions with increasing misorientation angle was observed experimentally. The magnetoresistance of bicrystal junctions has been calculated by taking into account the uniaxial anisotropy, which has allowed the contributions from the tunneling and anisotropic magnetoresistances to be separated. The largest tunneling magnetoresistance was observed on LCMO bicrystal junctions, in which the characteristic resistance of the boundary is higher than that in LSMO boundaries

POSSIBILITIES FOR IMPROVING THE SURFACE QUALITY OF STRUCTURAL STEELS, INVAR AND TITANIUM ALLOYS THROUGH REACTIVE ELECTROSPARK TREATMENT WITH ELECTRODES OF AN ALUMINUM-SILICON ALLOYS

In the rough and semi-pure processing of metal alloys, as well as in additive technologies, surface defects are often observed - the appearance of scratches, creases, recesses, incisions, pores, ridges, protruding particles, and other unevenness, undesirable spiral or concentric relief, traces of cutting edges of the tool and high roughness on the treated surface. In this work, the possibilities for improving the surface characteristics of materials such as steels, invar and titanium alloys with typical surface defects through reaction electrospark deposition (ESD) are investigated. A study of the conditions for the local formation of reactive phases and reduction of surface roughness during the electrospark modification was performed. Layering electrodes of low-melting Al-Si alloys were used. Their choice was made on the assumption that a liquid melt is formed in the process of ESD. It is expected that it will fill the recesses, pores and scratches and interact with the chemical elements contained in the substrate. The results of the studies of the change in the roughness, thickness and microstructural characteristics of the modified surfaces depending on the energy of the pulses and their influence on the wear resistance at friction are presented. A double effect has been achieved - a significant improvement in both the surface characteristics and the wear resistance of the modified surfaces. It was found that the improvement of surface quality and wear resistance was achieved as a result of partially burning the protrusions, filling the depressions with low melting electrode alloy and local synthesis of wear-resistant surface structures and phases obtained by the chemical interaction of the melt with the substrate. The energy parameters of the electric discharges, the process parameters, and the ESD conditions, suitable for the realization of the above phenomena, have been determined and optimized

Electron Transport in Manganite Bicrystal Junctions

The transport and magnetic properties of junctions created in La0.67Sr0.33MnO3 thin films epitaxially grown on substrates with a bicrystal boundary have been investigated. In tilted neodymium gallate bicrystal substrates, the NdGaO3(110) planes are inclined at angles of 12 degrees and 38 degrees. The temperature dependences of the electrical resistance, magnetoresistance, and differential conductance of the junctions at different voltages have been measured and analyzed. It has been found that the magnetoresistance and electrical resistance of the junction significantly increase with an increase in the misorientation angle, even though the misorientation of the easy magnetization axes remains nearly unchanged. The ratio of the spin-dependent and spin-independent contributions to the conductance of the bicrystal junction increases by almost an order of magnitude with an increase in the misorientation angle from 12 degrees to 38 degrees. The magnetoresistance of the junction increases with decreasing temperature, which is most likely associated with an increase of the magnetic polarization of the electrons. It has been shown that, at low (liquid-helium) temperatures, the conductance depends on the voltage V according to the law V-1/2, which indicates the dominant contribution from the electron-electron interaction to the electrical resistance of the junction. An increase in the temperature leads to a decrease in this contribution and an increase in the contribution proportional to V-3/2, which is characteristic of the mechanism involving inelastic spin scattering by surface antiferromagnetic magnons