Studies of the vortex related phase transition in YBCO thin films with strong in-plane anisotropy

We have studied the vortex-related phase transition in a number of YBCO thi n films that have in-plane anisotropy due to the c-axis lying at an angle t o the substrate normal. The critical parameters T-t, z, and v have been ext racted from the scaling of de I-V measurements made along the two principal transport directions in magnetic fields up to 1 tesla. The dependence of T -t upon the direction of the transport current in some classes of film and the very high z values cast doubt upon the established interpretation based simply upon a vortex liquid-vortex glass phase transition(1.)