MECHANICAL DISSIPATION AT DIFFERENT ORIENTATION OF MAGNETIC-FIELD IN HIGH-TC SUPERCONDUCTOR

The mechanical dissipation of (Bi0.9Pb0.1)2Sr2Ca2Cu3O10+y and YBa2Cu3O 7-x ceramics were measured as a function of the angle theta between th e orientation of the transverse magnetic field and the vibrating direc tion at fixed temperature and magnetic field with the vibrating reed t echnique. A relation between Q-1 (or f) and the angle theta, i.e. DELT AQ-1 (or DELTAf) approximately (H(a) cos theta)1.5 was found and this indicated that only the magnetic field component parallel to the vibra ting direction H(a) cos theta gives rise to the enhancement of interna l friction and resonant frequency in ceramic sample. The anisotropic d eformation of flux-line-lattice is used to explain the observed result s.