Persons

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The influence of morphology of metal-ferroelectric-metal interfaces structures on their electric properties has been investigated. The experimental researches of buffer layers influence and the methods of the electrode deposition on the morphology on the ferroelectric film have been conducted. The theoretical analysis of the dielectric properties has been performed on the basis of the experimental data for heterostructures, however, the final assessment has been made using the mathematical modeling methods.

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A series of studies for explaining the role of superexchange interactions in formation of the ferromagnetic state of cobaltites of LaSrCoMe O(Me = Cr, Ga, Fe) systems and LaSrMnMO (M - Nb, Mg) manganites with the perovskite structure have been performed. The obtained results have testified that ferromagnetism in cobaltites can be realized within the homovalent state of the cobalt ions. The initial compound ( x = 0) is a ferromagnetic ( T =247 K) with the saturation magnetization close to 2µB (at T = 30 K) per formula unit (at T = 30 K). It has been shown that the chemical substitution of cobalt for chromium ones decreases the spontaneous magnetization down to 0.3µB (at x = 0.2), while the substitution of cobalt for iron ions ( x = 0.2) does not modify the magnetization. The obtained data are interpreted in the model of positive superexchange interactions between cobalt and iron and the negative ones between cobalt and chrome. It has been demonstrated that LaSrMnNbO is ferromagnetic ( T = 145 K) with magnetic moment 3.1 µ/Mn at 10 K. No evidence of cooperative orbital ordering in manganite compounds has been revealed. Partial chemical substitution of Nb ions for Mg ones leads to formation of Mn ions, while it does not improve the ferromagnetic state. The intensification of structural distortions diminishes the ferromagnetic component. It has been assumed that the ferromagnetic state is caused by significant hybridization of ėg orbitals of manganese and oxygen ions thus strengthening the positive component of superexchange interactions.

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The results of studies on the film composites, based on polyvinylidene fluoride with the carbon nanotubes, by the dielectric relaxation spectroscopy have been presented. For the composite samples with the content of nanotubes exceeding 0.5 wt% the nonlinear current-voltage characteristics have been obtained. The concentration dependences of conductivity of the composites have been studied and, also, the percolation threshold for the samples being investigated has been determined. It has been shown that an insignificant increase of the composites electric conductivity is observed even at 0.2 wt%, while introducing 1 wt% of nanotubes the electrical conductivity becomes 3 orders higher and at more than 3 wt% it is 7 orders higher compared to the non-filled polymer. This verifies the perspectives of using the carbon nanotubes for creation of the electro-conducting composites and film materials based on polyvinylidene fluoride.

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