VORTEX DYNAMICS AND INSTABILITIES IN LAYERED AND HOMOGENEOUS TA GE SUPERCONDUCTORS/

We present measurements of a dynamically induced instability in the vo rtex state of an amorphous multilayer and a single alloy layer of Ta/G e, The critical vortex velocity shows quantitative agreement with the predictions of Larkin and Ovchinnikov calculated using parameters dete rmined independently from the normal state resistivity data. Both samp les show a weak field dependence in the critical velocity implying a v elocity dependent pinning force in the vortex solid state and a broade ning of the transition resulting from the velocity distribution in the liquid state.