Effect of External Current on the Magnetization of Non-Ideal Type II Superconductors

Disclosure of hidden magnetic moments in low and highTchysteretic and semi-reversible type II superconductors during warming toTc

“…These values are then independent of the magnitude of H a and whether H a has ascended or descended from H rev to the specific location along the bridges where the corresponding flux profiles are encountered. However for Kim-like [36][37][38][39] dependences of j c on B, and I M = 0, we could not find, after detailed and extensive calculations, any profiles where conservation of flux allowed r i (x i ) to remain fixed as j c (B, T ) collapsed. Our calculations showed this interface to either migrate to the surface or to the centre as j c (B, T ) diminished.…”

“…r i migrates from r = R to r = 0 as M is made to cross from one envelope to the opposite. This migration of r i as H a swings from H rev can readily be calculated by exploiting the critical state concept [31,[33][34][35][36][37][38][39] and some convenient and appropriate function for j c (B, T ) and I M (H a , T 0 ). The interface r i will also migrate inwards or outwards when the sample is warmed to T c with H a fixed and M initially situated along a bridge between the hysteresis envelopes.…”

“…The family of theoretical magnetization curves corresponding to that observed in our very hysteretic samples is calculated using the critical state model [33][34][35][36][37][38][39]. Here for convenience and simplicity we exploit the well known Kim-Anderson expression [37] for the dependence of the critical current density on B, namely,…”

“…Figure 26 displays the basic magnetization curves for the BiSCCO slab at 77 K and figure 27 shows the corresponding calculated curves. In these calculations we took j c ∝ 1/ √ B (denoted the Yasukochi approximation [39]) and H c1 independent of H a > H c1 , hence q = 0 in equation (8).…”