SUPPRESSION OF MAGNETIZATION BY A SMALL TRANSVERSE AC MAGNETIC FIELD

Abstract

One efficient method to investigate the vortex matter in the high-temperature superconductors is to measure the magnetization while shaking vortices by applying a transverse ac magnetic field, Hac. When a small transverse Hac is superposed with the dc magnetic field, the vortices will experience time-varying torque by ac field. This vortex shaking gives rise to effective reduction of pinning energy, which in turn gives rise to a rapid relaxation of the irreversible magnetization. This experimental approach has been used to study the nature of the anomalous magnetization peak in a N 2-annealed Tl 2 Ba 2 CuO single crystal. Shaking vortex unveiled the otherwise unobserved anomalous magnetization peak; when Hac=0, no noticeable structure in the magnetization loop was observed, but with vortex shaking by Hac, the magnetization loop deformed to exhibit the anomalous magnetization peak. The evolution of the anomalous peak with Hac can provide a clue to the understanding of the underlying mechanism for the occurrence of the peak.