Mixed-state microwave resistivity in RE–BaCuO films

We present measurements of the microwave complex resistivity at 48 GHz in REBa2Cu3O<f>7−δ</f> thin films (RE=Y, Sm) in moderate magnetic fields (<f>μ0H<0.8</f> T) and above 60 K. The measured complex resistivity gives valuable information for the study of vortex dynamics. We show that the field dependence of the microwave resistivity has rather different behaviours in YBa2Cu3O<f>7−δ</f> and SmBa2Cu3O<f>7−δ</f>. By applying the conventional model of vortex motion, the data in SmBa2Cu3O<f>7−δ</f> would yield exotic behaviours for the vortex parameters. However, taking into account the enhanced field-induced change in quasiparticle density in a superconductor with lines of nodes in the gap, the vortex part of the response behaves similarly in YBa2Cu3O<f>7−δ</f> and SmBa2Cu3O<f>7−δ</f>. [Copyright &y& Elsevier]