Remanent magnetization of ceramic and single-crystal high-T-c superconductors in tilted magnetic fields

Dependence of the remanent magnetization (M(r)) anisotropy on the structure and shape of the superconductor and on the magnetizing procedure was studied for a number of high-T-c superconductor ceramics and single crystals. The experiments were done by means of a vibrating-sample magnetometer with a rotatable sample holder. It was found that the main contribution to the anisotropic behavior of M(r) is due to the surface screening currents, and therefore the anisotropy is subject to variation when sample shape is changed. The question is resolved, why the effective demagnetization factors for decoupled ceramic samples are different from those calculated in the inscribed-ellipsoid approximation. Influence of inhomogeneous grain magnetization and global bulk currents on the angular dependencies of M(r) in ceramic samples is investigated. The evolution of remanence in YBCO single crystals with an increase of the magnetizing field is described within an extended Bean model. (C) 1996 American Institute of Physics.