Biphasic composite materials were synthesized near the La0.7Sr0.3MnO3-based percolation threshold and the second phase, which is an inorganic or organic compound — polyvinyl acetate, paraffin, carboxymethylcellulose, sucrose, and ultrafine silver particles. For composites with an organic matrix, the magnetoresistance values ​​do not exceed 2%, and for composites with silver particles - 8%. The values ​​of isotropic negative magnetoresistance for ceramic samples of 80% LSMO / 20% GeO2 (mass%) reach 13% in a 15 kOu magnetic field with a sensitivity of about 1% / ke in the low-field region. High chemical and radiation stability of these glass composites should be noted. The magnetoresistive properties of such compounds slightly decreased after 60 days of being in water with a salinity of 35 ppm. Composites of 80% LSMO / 20% GeO2 were exposed to X-rays with a dose of 7 Sv from the Co57 source. The magnetoresistive properties and electrical resistance of these composites did not change after that.

Keywords: lanthanum strontium manganite, ceramic two-phase material, one-step synthesis, radiation exposure, magnetoresistance, percolation threshold, dielectric constant, barrier layer, spin-dependent tunneling, spin polarization

The electrical properties of composites based on La0.7Sr0.3MnO3 (LSMO) synthesized at the percolation threshold have been studied: LSMO / Li4P2O7, LSMO / Sb2O3, LSMO / GeO2. The activation energies of these compounds have been determined. New ceramic materials with silver interlayers between LSMO manganite crystallites have been synthesized. The current-voltage characteristics for the LSMO / GeO2 series are given. The nonlinearity of the characteristics is most pronounced for compositions near the percolation threshold, 85% LSMO / 15GeO2.

Keywords: lanthanum strontium manganite, composite material, ceramics, one-step synthesis, magnetoresistance, percolation threshold, dielectric constant, barrier layer, tunneling, spin polarization

A new class of materials is proposed that change their dielectric permittivity as a function of the magnetic field strength. Such materials are two-phase composites of composition La0.7Sr0.3MnO3 / I, where I is the isolating phase, Li4P2O7 or GeO2. The ratio of components is close to the percolation threshold: from 10% to 20% by weight. Dielectric properties have been studied in the frequency range of the measuring field from 1 kHz to 1 MHz in magnetic fields from 0 to 15 kOe. Samples have an inductive impedance, their permittivity is negative. In a magnetic field, the permittivity increases in absolute value and at room temperature the values of the magnetodielectric coefficient reach 28%.

Keywords: lanthanum strontium manganite, composite material, ceramics, one-step synthesis, magnetoresistance, percolation threshold, dielectric constant, barrier layer, tunneling, spin polarization

Based on our own, as well as literary experimental data, the analysis of the Influence of a barrier material used to create heterogeneous composites based on La0.7Sr0.3MnO3 on their magnetoresistive properties is carried out. Such composites differ in existence of an isotropic negative magnitorezistivnost (MR) connected from backs - dependent tunneling of carriers in magnetic field. The largest value MR up to 15% in the field of 15 kOe are shown when using glass-like GeO2 oxide at a percolation ratio of components.

Keywords: lanthanum strontium manganite, composite material, ceramics, one-step synthesis, magnetoresistance, percolation threshold, dielectric constant, barrier layer, tunneling, spin polarization

Lanthanum strontium manganite La0,67Sr0,33MnO3 which has a high spin polarization of the carriers has been used to create composite materials with different barrier materials - GeO2, Li4P2O7, C. The magnetoresistive properties of the synthesized ceramics at room temperature have been investigated. It has been found that the magnetoresistive isotropic negative values ​​for samples with germanium oxide at room temperature in a magnetic field of 18 kOe reach a value of 15%, with the barriers of lithium pyrophosphate - 16%. It has been determined that the samples which contain 10-85% graphite at a field of 15 kOe exhibit positive magnetoresistance reaching a value of 15% .

Keywords: lanthanum strontium manganite, composite material, ceramics, magnetoresistance, X-ray diffraction, microstructure, barrier layer, tunneling, percolation transition, spin polarization, the Seebeck effect

Composites La0,67Sr0,33MnO3 (SiO2, Sb2O3) with different weight ratios have been synthesized. Their magnetoresistive and dielectric properties have been investigated. It has been established that in the frequency range from 10 to 106 Hz for SiO2 concentration of 10% the colossal magnitudes of the dielectric constant ( ~ 4 • 104) take place. The values of the negative isotropic magnetoresistance for samples with silica at room temperature is 8.6%, with abarriers of antimony oxide reaches 12%, which makes it possible to use such materials in spintronics.

Keywords: Magnetoresistance, colossal dielectric permittivity, glass composites, X-ray diffraction, spin polarization, barrier layers, tunneling, microstructure, dielectric spectrum, Maxwell-Wagner effect.