Anisotropy of magnetization and flux pinning at 77 K in melt textured YBCO

We have studied the zero-field cooled (MZFC), field cooled (MFC) and remanent magnetization (MREM) variations as a function of orientation and field at 77 K in melt textured Y1Ba2Cu3O7-x superconductors. We find a lesser preference of the remanent flux for the c-axis, as compared with low temperatures, which is interpreted as being due to more three-dimensional behaviour of vortices. The three-dimensional behaviour is more pronounced at higher fields. Field cooled magnetization does not in general satisfy the relation MFC=MZFC+MREM, indicative of lack of rigidity and continued depinning of vortices during the (field cooled) magnetization rotation process. The differences between MFC and MZFC+MREM are discussed as a function of field and rotation angle. Data are explained in terms of weaker pinning and decreased effects of anisotropy as compared with low temperatures. We also find evidence for intergrain flux pinning at H=10 Oe in zero-field cooled magnetization. (author)