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Flux dynamics and vortex phase diagram of the new superconductor $MgB_2$

H. H. Wen·S. L. Li·Z. W. Zhao·Y. M. Ni·Z. A. Ren·G. C. Che·Z. X. Zhao
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Abstract

Magnetic critical current density and relaxation rate have been measured on $MgB_2$ bulks from 1.6 K to $T_c$ at magnetic fields up to 8 Tesla. A vortex phase diagram is depicted based on these measurement. Two phase boundaries $H_{irr}^{bulk}(T)$ and $H_{irr}^{g}(T)$ characterizing different irreversible flux motions are found. The $H_{irr}^{bulk}(T)$ is characterized by the appearance of the linear resistivity and is attributed to quantum vortex melting induced by quantum fluctuation of vortices in the rather clean system. The second boundary $ H_{irr}^g(T) $ reflects the irreversible flux motion in some local regions due to either very strong pinning or the surface barrier on the tiny grains.

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H. H. Wen, S. L. Li, Z. W. Zhao, Y. M. Ni, Z. A. Ren, G. C. Che, Z. X. Zhao. 2001-03-26. Flux dynamics and vortex phase diagram of the new superconductor $MgB_2$. https://doi.org/10.1016/s0921-4534(01)00936-4

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