Microwave vortex dynamics in Tl-2212 thin films
arXiv:0710.3488 · doi:10.1016/j.physc.2007.11.063
Abstract
We present measurements of the effective surface impedance changes due to a static magnetic field, $ΔZ(H,T)=ΔR(H,T)+\rmi ΔX(H,T)$, in a Tl-2212 thin film with 103 K, grown on a CeO buffered sapphire substrate. Measurements were performed through a dielectric resonator operating at 47.7 GHz, for temperatures 60 K and magnetic fields T. We observe exceptionally large field induced variations and pronounced super-linear field dependencies in both and with in almost the whole range explored. A careful analysis of the data allows for an interpretation of these results as dominated by vortex dynamics. In the intermediate-high field range we extract the main vortex parameters by resorting to standard high frequency model and by taking into proper account the creep contribution. The pinning constant shows a marked decrease with the field which can be interpreted in terms of flux lines softening associated to an incipient layer decoupling. Small vortex viscosity, by an order of magnitude lower than in Y-123 are found. Some speculations about these findings are provided.
pdfTeX, 4 pages, 3 figures, VORTEX 2007 proceedings, to appear in Physica C