Vortex state microwave resistivity in Tl-2212 thin films

Abstract

We present measurements of the field induced changes in the 47 GHz complex resistivity, $\Delta \tilde{\rho }(H,T)$, in Tl${}_2$Ba${}_2$CaCu${}_2$O${}_{8+x}$ (TBCCO) thin films with $T_c\simeq$ 105 K, prepared on CeO${}_2$ buffered sapphire substrates. At low fields (${\mu }_{0}H<$10 mT) a very small irreversible feature is present, suggesting a little role of intergranular phenomena. Above that level $\Delta \tilde{\rho }(H,T)$ exhibits a superlinear dependence with the field, as opposed to the expected (at high frequencies) quasilinear behaviour. We observe a crossover between predominantly imaginary to predominantly real (dissipative) response with increasing temperature and/or field. In addition, we find the clear scaling property $\Delta \tilde{\rho }(H,T)=\Delta \tilde{\rho }[H/H^{\ast }(T)]$, where the scaling field $H^{\ast }(T)$ maps closely the melting field measured in single crystals. We discuss our microwave results in terms of loss of flux lines rigidity.

8 pages, 3 figures, proceedings of 9th HTSHFF, accepted for publication on J. Supercond