Fizika Nizkikh Temperatur: Volume 45, Number 11 (November 2019), p. 1360-1365    ( to contents , go back )

Berezinski–Kosterlitz–Thouless transition in bulk nanocomposites superconductor–ferromagnet MgB2:(La,Sr)MnO3

A.I. D’yachenko

G.V. Kurdyumov Institute for Metal Physics, National Academy of Sciences of Ukraine, 36 Academician Vernadsky Blvd., Kyiv 03142, Ukraine

V.Yu. Tarenkov, and V.N. Krivoruchko

O.O. Galkin Donetsk Institute for Physics and Engineering, National Academy of Sciences of Ukraine, 46 Nauki Ave., Kyiv 03028, Ukraine
E-mail: krivoruc@gmail.com

Received June 12, 2019, published online September 27, 2019

Abstract

The results of studies of transport characteristics of MgB2:La0.67Sr0.33MnO3 (LSMO) nanocomposite with a volume content of the components 3:1 are presented. It was established experimentally that temperature behavior of the resistance of the bulk MgB2:LSMO samples under the transition to a superconducting state is described by the Berezinsky–Kosterlitz–Tauless (BKT) model for two-dimensional superconductors. The observed features of the transport properties are most likely due to two characteristic spatial scales in the system: (i) a significant difference in geometric dimensions of the components (micronsized particles of MgB2 and nanoparticles of LSMO) and (ii) the coherence length of triplet superconducting state of half-metal manganite LSMO being in contact with MgB2. In such nanostructures, resistive losses are due to the processes of current flow through ferromagnetic LSMO nanogranules covering MgB2 microgranules. With temperature decreasing, in two-dimensional (surface) superconducting LSMO layers the BKT transition is realized.

Key words: superconductor–ferromagnet composites, Berezinski–Kosterlitz–Thouless transition.

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