Angular dependence of magnetic relaxation and remanent magnetization on YBCO/PBCO super-lattice and YBCO thin film

We measured the angular dependence of magnetic relaxation and remanent magnetization at various temperatures on a YBCO/PBCO superlattice and a YBCO thin film to investigate the fluctuation of the anisotropy of flux pinning. The measuring temperatures were from 20 K to T_c,onset and the applied magnetic field was 1000 Oe. The angles between the applied magnetic field and the c-axis of superlattices were 0°, 30°, 45°, 60°,.... In the measurement of the angular dependence of remanent magnetization, the angles between the magnetometer and c-axis were from -90° to 90°. The Anderson-Kim model was introduced to derive the pinning potential. It was observed that only the component of applied magnetic field along c-axis of the samples contributed to flux pinning and we also obtained the relation, Mθ = M∥ cosθ, where M∥ is the magnetization along the c-axis. The causes are discussed.