Vortex state microwave resistivity in Tl-2212 thin films

We present measurements of the field induced changes in the 47 GHz complex resistivity, ρ(H,T), in Tl2 Ba2CaCu2 O8+x (TBCCO) thin films with T c 105 K, prepared on CeO2 buffered sapphire substrates. At low fields (μ0 H < 10 mT) a very small irreversible feature is present, suggesting a little role of intergranular phenomena. Above that level ρ(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 ρ(H,T) = ρ[H/H*(T)], where the scaling field H∗(T) maps closely the melting field measured in single crystals. We discuss our microwave results in terms of loss of flux lines rigidity.