Kononenko V. Transport properties of magnesium diboride-manganite nanocomposites

In the dissertation, transport characteristics of nanocomposite made of ferromagnetic lanthanum manganite nanoparticles and superconducting diboride magnesium micrograins were established. Experimentally showed that in the normal and superconducting states character of a percolation network formation in the nanocomposites are different. At room temperature, the effect of grain size of the components (micro and nano grains component) determines the transport characteristics of nanocomposite (current-voltage dependence, the percolation threshold). When temperature is below the critical one of the superconducting transition of magnesium diboride, transport properties of the nanocomposites (superconducting transition temperature, critical current value, the current-voltage characteristics) are determined by proximity effects due to formation of weak contacts superconductor-manganite-superconductor. The effect of hydrostatic pressure on the transport properties of diboride magnesium- manganite composites proved that a weakly coupled medium is established in the system.