Thermally-activated current transport in MgB_2 films

Abstract

Thermally-activated flux flow (TAFF) resistivity above the irreversibility field is reported for two different c-axis textured MgB_2 superconducting films. Transport measurements at different perpendicular magnetic fields 0 < B < 9 T and temperatures from 5 to 40K reveal TAFF Ohmic resistivity described by the Arrhenius law with the quadratic field dependence of the activation energy. Our transport measurements on bulk MgB_2 ceramic samples also show the TAFF behavior, but do not show the quadratic field dependence of U(T,B). We explain our results in terms of thermally-activated drift of pre-existing quenched dislocations in the vortex lattice. Our results indicate that thermal fluctuations can be essential in determining the irreversibility field in MgB2 though to a much lesser extent than in high-temperature superconductors.

32 Pages, 8 figures, to be published in Physical Review B

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Cited by in corpus (7)

• Limits of the upper critical field in dirty two-gap superconductors
• Anisotropic Connectivity and its Influence on Critical Current Densities, Irreversibility Fields, and Flux Creep in In-Situ-Processed MgB2 Strands
• Magnetic field dependence of vortex activation energy: a comparison between MgB2, NbSe2 and Bi2Sr2Ca2Cu3O10 superconductors
• Upper critical field, superconducting energy gaps, and Seebeck coefficient in La0.8Th0.2OFeAs
• Reaction method control of impurity scattering in C-doped MgB2, proving the role of defects besides C substitution level
• Intergrain connectivity and resistive broadening in vortex state: a comparison between MgB2, NbSe2 and Bi2Sr2Ca2Cu3O10 superconductors
• The Anisotropy of Thermal Activation Energy of 2H-NbS${}_2$