Funct. Mater. 2015; 22 (3): 332-337.

http://dx.doi.org/10.15407/fm22.03.332

Phase H-T-diagram for MgB2 granular BCS-superconductor in weak magnetic fields

V.V.Derevyanko, T.V.Sukhareva, V.A.Finkel, Yu.N.Shahov

National Science Center ”Kharkiv Institute of Physics and Technology,” National Academy of Sciences of Ukraine, 1 Akademichna Str., 61108 Kharkiv, Ukraine

Abstract: 

For the purpose of plotting the H-T diagram for MgB2 granular superconductors, the behavior of electrical resistivity-versus-temperature dependences were studied at ~35 to ~45 K in external magnetic fields with magnetic field strengths Hext up to ~2 kOe. The effect of increasing the superconductivity transition width ΔTc at increased Hext has been revealed. A model has been developed for superconductivity transitions in a two-level system. The data obtained allowed establishing the existence of a weak links system in MgB2 granular superconductors.

Keywords: 
MgB<sub>2</sub>, HTSC, two-level system, H-T-phase diagram, critical fields, resistivity.
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