Anisotropy in Bi 2 Sr 2 CaCu 2 O 8+ x Films at Microwave Frequencies: Enhancement of Dissipation in Parallel Magnetic Field

Abstract
Magneto-resistive measurements at microwave frequencies have been carried out in c-oriented Bi2Sr2CaCu2O8+x films. When the angle between the magnetic-field direction and the (a, b)-plane is varied a large anisotropy is observed in the microwave absorption. In the range 4° < ≤ 90°, the dissipation scales as H sin , but below 4° an anomalous enhancement of dissipation is present. The behaviour of the enhancement is measured as a function of the temperature in the range (70 ÷ 85) K.