Journal of Physics and Chemistry of Solids vol:67 issue:1-3 pages:419-423
We have investigated the magnetisation response of a La2-xSrxCuO4 epitaxial thin film at microwave frequencies as a function of temperature and external magnetic field using a copper loop as a resonator. At low field and low temperature a single negative peak and a sudden jump in the time and microwave frequency dependence of the magnetisation are observed for certain frequency values. Near T-C, sharp negative peaks appear at different frequencies. With the increase of the magnetic field, the same structure of peaks appears at lower temperature. These phenomena are not observed when identical measurements are made either without radiation or when the sample is in the normal state. We attempt to identify them as the combined result of the vortex dynamics, a screening effect at the sample edge and a vortex shaking process caused by the microwave field. (c) 2005 Elsevier Ltd. All rights reserved.