The Berezinskii–Kosterlitz–Thouless transition in bulk MgB2:(La,Sr)MnO3 superconductor-ferromagnetic nanocomposites

The results of studying the transport characteristics of the MgB2:La0.67Sr0.33MnO3 (LSMO) nanocomposite with a 3:1 volume content of components are presented. The experiments have shown that the temperature behavior of resistance of bulk MgB2:LSMO samples during the transition to the superconducting state is described by the Berezinskii–Kosterlitz–Thouless (BKT) model for 2D superconductors. The observed features of the transport properties are most likely due to two characteristic spatial scales in the system: 1) a significant difference between the geometrical dimensions of the constituent components (micrometer-sized MgB2 particles and LSMO nanoparticles), and 2) the coherence length of the triplet superconducting state of half-metal manganite LSMO contacting with MgB2. Resistive losses in such nanostructures are due to the flow of current through ferromagnetic LSMO nanogranules that cover MgB2 microgranules. As temperature decreases, the BKT transition occurs in 2D (surface) superconducting LSMO layers.The results of studying the transport characteristics of the MgB2:La0.67Sr0.33MnO3 (LSMO) nanocomposite with a 3:1 volume content of components are presented. The experiments have shown that the temperature behavior of resistance of bulk MgB2:LSMO samples during the transition to the superconducting state is described by the Berezinskii–Kosterlitz–Thouless (BKT) model for 2D superconductors. The observed features of the transport properties are most likely due to two characteristic spatial scales in the system: 1) a significant difference between the geometrical dimensions of the constituent components (micrometer-sized MgB2 particles and LSMO nanoparticles), and 2) the coherence length of the triplet superconducting state of half-metal manganite LSMO contacting with MgB2. Resistive losses in such nanostructures are due to the flow of current through ferromagnetic LSMO nanogranules that cover MgB2 microgranules. As temperature decreases, the BKT transition occurs in 2D (surface) superconducting LSMO layers.