Thin superconducting disk with field-dependent critical current: Magnetization and ac susceptibilities

Article

关键词: CRITICAL-CURRENT-DENSITY;    CRITICAL-STATE MODEL;    II SUPERCONDUCTORS;    FLUX-PENETRATION;    FILMS;    YBA2CU3O7-DELTA;    LOSSES;    RINGS;    CREEP;   

DOI  :  10.1103/PhysRevB.61.9699

来源: SCIE

【 摘 要 】

Magnetization hysteresis loops and the ac susceptibility chi=chi'+i chi of a superconducting thin disk are calculated in the critical-state model assuming a field-dependent critical current density J(c)(B). The results are obtained by solving numerically the set of coupled integral equations for the Bur and current distributions [Phys. Rev. B 60, 13 112 (1999)] for a disk placed in a perpendicular applied field B-a. From the magnetization curves the range of fields where the vertical width of the loop Delta M(B-a) relates directly to J(c)(B-a) is determined. The susceptibility is analyzed in the limits of small and large ac-field amplitudes B-am, and also as a parametric relation chi(chi') Comparing our results with experimental data for chi(chi') shows that by taking the B dependence of J(c) into account the agreement Improves dramatically, in particular at small \chi'\ (large field amplitudes). We show that the asymptotic behavior for large B-am changes from chi' proportional to B-am(-3/2) and chi proportional to B-am(-1) for the Bean model, to chi' proportional to B-am(-3) and chi proportional to B-am(-2) for J(c) decreasing with \B\ as \B\(-1) or faster. For small B-am the behavior can always be described by an effective Bean model with a renormalized J(c). We also find that in the chi(chi') plot the peak of chi increases in magnitude and shifts towards chi' = 0 when J(c) decreases with \B\. This allows an easy experimental discrimination between a Bean model behavior, one with J(c)(B), and one where flux creep is an ingredient.

【 授权许可】

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