Magnetic relaxation on bridges between the envelopes of major hysteresis loops of type II superconductors

The initial decay rate R = d(M)/d(j/j(0)) along the envelope of the major hysteresis curves and along bridges between these envelopes is examined in the framework that the current density of the relaxing field profiles initially exists in a critical state and can be described by a product function where j(c) = j(0)(T, t)f[H(x), T, t)] with dj(0)/dt assumed independent of H. This simple model is shown to reproduce the pertinent observations of Beasley et al and Kwasnitza and Widmer. The model also predicts interesting structure in the curves of R versus H along bridges where H changes sign during its swing between the magnetization envelopes when j(c) descends steeply with H.