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

M. J. Qin·X. L. Wang·H. K. Liu·S. X. Dou
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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.

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M. J. Qin, X. L. Wang, H. K. Liu, S. X. Dou. 2001-04-06. Dependence of the flux creep activation energy on current density and magnetic field for MgB2 superconductor. https://doi.org/10.1103/physrevb.64.060505

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