ANISOTROPIC VORTEX CROSS-FLUX EFFECTS IN GRAIN-ORIENTED YBA2CU3O7

After cooling to 4.2 K in a field H(cool) parallel (or normal) to the c axis and then removing H(cool), the sample was subjected to an increasing field H normal (or parallel) to c and the longitudinal and transverse magnetizations relative to H were measured simultaneously. The vortex flux produced by H(cool) along c persists and inhibits the creation by H of vortex flux in the a-b plane. However, the creation of the latter does not require a threshold value of H. The vortex flux produced by H(cool) in the a-b plane diminishes rapidly with increasing H along c, and there are essentially no cross-flux effects. Thus, these effects are largely governed by the strength of the initial flux pinning, which is highly anisotropic.