MAGNETIC AFTER EFFECTS IN A TYP-II SUPERCONDUCTOR

Résumé
Les effets de "bascule et reptation", phénomène connu du comportement des matériaux ferromagnétiques /1/ soumis à un champ alternatif et un champ magnétique constant, existent également dans les supraconducteurs de type II.

Abstract
Periodically swept minor hysteresis loops of type-II superconductors show a creep effect, that consists of a) a displacement and b) a tilting of the minor loop. The initial dependence of the creep on the number of swept minor hysteresis cycle can be described by a logarithmic law, deviations occur at high cycle numbers. The effect appears not to be due to simple thermal relaxation : for not too fast sweep rates no for dependence of creep rate on the total measuring time was found within accuracy of measurement. Moreover the flux density gradient appears to increase with increasing cycle number in the region of the sample which is subject to periodic magnetization change indicating a more effective pinning of flux lines.