ANGULAR-DEPENDENCE OF LOW-FIELD REMANENT MAGNETIZATION IN YBA2CU3O7-DELTA

The remanent magnetization in single crystals of YBa2Cu3O7-delta has b een measured at 77 K as a function of the applied magnetic field orien tation relative to the sample. The remanent magnetization was generate d by an externally applied field of 10 G. After correction for the dem agnetization factor due to the shape of the crystal samples, it is fou nd that the remanent magnetization, plotted as a function of the inter nal field, has two distinct slopes. Furthermore, for the same internal field, the remanent magnetization in the a-b-plane is shown to be lar ger than that along the c-axis. The experimental data suggest that at low internal fields the remanent magnetization prefers to orient in a direction parallel to the a-b-plane. We discuss these findings in term s of relevant vortex-flux penetration and flux pinning mechanisms.