ANGLE-DEPENDENT MICROWAVE MAGNETO-DISSIPATION IN BI2SR2CACU2O8 FILMS - QUASI-2D ANGULAR SCALING PROPERTIES

We have measured the orientational dependence of the magnetic-field in duced microwave dissipation at 21 GHz in a Bi2Sr2CaCu2O8+x epitaxial f ilm, by means of a cavity technique. The dissipation is measured as a function of the external magnetic field H and of the angle (curly thet a) between H and the (a, b) planes, at fixed temperatures. Measurement s were taken in the range 49-81 K. Apart from a narrow (Delta(curly th eta)approximate to 0.5 degrees) angular range close to the parallel or ientation, the strongly anisotropic dissipation can be successfully sc aled over the orthogonal-field curve with a simple rescaling of the ma gnetic field: H --> H/f(curly theta). Best scaling is obtained with th e quasi-two-dimensional (quasi-2D), thin-film expression for f(curly t heta). One single parameter, the anisotropy ratio epsilon, is used in the scaling. It is found that epsilon increases with temperature, cons istent with the quasi-2D result, which gives a quantitative fitting fo r the data. The anisotropy ratios so obtained are compared with those previously obtained by the angular scaling of the critical currents in a sample from the same batch. The quantitative agreement between the two sets is excellent, strongly indicating that the same scaling prope rties apply in Bi2Sr2CaCu2O8 for very different dissipative properties .