Temperature dependence of the material parameters in the Kim-Anderson critical-state model for a melt-processed YBa2Cu3O7

Abstract

The magnetic response of a melt-processed YBa2Cu3O7 was measured to make clear the physical meanings of the parameters k and B0 in the Kim-Anderson critical-state model where the critical current density Jc is assumed to be a function of the local internal magnetic-flux density Bi, Jc(Bi) = k/(B0 + |Bi|). The isothermal magnetization curves of the sample were measured in the wide temperature region below the critical temperature, and the parameters were selected so as to fit the calculated curve to the observed one at each temperature. We found that k and B0 are proportional to (1 − T/Tc)γ, where γ = 2.5 – 3.0 and to (1 −T/Tc)1.5, respectively. We propose that B0 approximately corresponds to the irreversibility magnetic-flux density Birr.