SURFACE BARRIERS, IRREVERSIBILITY LINE, AND PANCAKE VORTICES IN AN ALIGNED HGBA2CA2CU3O8+DELTA SUPERCONDUCTOR

The irreversible magnetic properties of a magnetically aligned HgBa2Ca2Cu3O8+delta superconductor have been investigated as a function of temperature and magnetic field, for both H parallel to c axis and H parallel to ab plane. Experimental results for the magnetic hysteresis Delta M, the field of first flux penetration H-p, and the irreversibility line with H parallel to c are well described by recent theory [L. Burlachkov et al., Phys. Rev. B 50, 16770 (1994)] for thermally activated penetration of a surface barrier by pancake vortices. Near 85 K, the system crosses over from two-dimensional to three-dimensional line vortices, from which we extract estimates for the mass anisotropy parameter epsilon.