Magnetization of a superconductor: Results from the critical-state model

Abstract

The field suppression of the critical current density in superconductors, jc, is modeled within the critical-state theory by the modified Kim-Anderson relation, jc(B,T)=α(T)/(B+h)n, with α, h, and n being phenomenological parameters. This quasistatic approach of analyzing the flux evolution in a sample under varying external field allows us to explain a few ubiquitous, experimentally known results: the occurrence of a peak in the M(H) hysteresis at low fields and the saturation of the remanent magnetization as a function of sample size for larger sample sizes. In the present work, the critical-state concept is extended to describe the flux-profile evolution under temperature changes. Within this approach, the temperature dependences of the zero-field-cooled magnetization and of the remanent magnetization are calculated and compared with measurements performed on single crystals of Bi2Sr2CaCu2O8, UPt3, and URu2Si2. This approach has been applied for computing magnetocaloric effects in a superconductor exposed to a changing external field. Estimates on the value and temperature dependence of the field for flux jumps are given for heavy-fermion superconductors and they are compared with the known results for URu2Si2.

Source-reported materials — not catalogue approval

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