Dependence of the flux creep activation energy on current density and magnetic field for MgB2 superconductor

Abstract

Systematic ac susceptibility measurements have been performed on a MgB${}_2$ bulk sample. We demonstrate that the flux creep activation energy is a nonlinear function of the current density $U(j)\propto j^{-0.2}$, indicating a nonlogarithmic relaxation of the current density in this material. The dependence of the activation energy on the magnetic field is determined to be a power law $U(B)\propto B^{-1.33}$, showing a steep decline in the activation energy with the magnetic field, which accounts for the steep drop in the critical current density with magnetic field that is observed in MgB${}_2$. The irreversibility field is also found to be rather low, therefore, the pinning properties of this new material will need to be enhanced for practical applications.

11 pages, 6 figures, Revtex format

References in corpus (8)

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• Lattice Properties of MgB2 versus Temperature and Pressure
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• Effects of Fission-Fragment Damage on Vortex Dimensionality in Silver-sheathed Bi2Sr2Ca2Cu3Ox Tapes
• Complete electronic phase diagram and enhanced superconductivity in fluorine-doped PrFeAsO1-xFx
• Establishment of global phase coherence in a highly disordered fractal MgO/MgB2 nanocomposite: Roles of interface, morphology and defect