ANISOTROPY IN MAGNETIC HYSTERESIS OF BSR2CAN-1CUNO2N+3 (N = 3,4,5) SUPERCONDUCTORS

We investigated the anisotropy of magnetization. hysteresis Delta M at various temperatures for magnetically grain aligned samples of BSr2Ca n-1CunO2n+3 [B-12(n - 1)n, n = 3, 4, 5] superconductors. In the low-te mperature region, Delta M-parallel to with magnetic field parallel to the c-axis is larger than Delta M-perpendicular to with magnetic field perpendicular to the c-axis. When temperature is increased, crossover between Delta M-parallel to and Delta M-perpendicular to occurs at a certain magnetic field, i.e., Delta M-parallel to < Delta M-perpendicu lar to for an applied field higher than the critical value. This cross over was observed for all members of the series and seems to be caused by different vortex structures corresponding to magnetic fields paral lel and perpendicular to the c-axis. In-plane critical current density and irreversibility field corresponding to it were calculated from De lta M-parallel to. Their temperature variations suggest B-1223<B-1245< B-1234 as the order of anisotropy of electronic structures.