Anisotropy in magnetic hysteresis for (Cu,V)Sr2Can-1CunO2n+3 (n = 3, 4) superconductors

We determined anisotropies of superconducting properties of high-T-c superconductors, (Cu,V)Sr2Can-1CunO2n+3 [(Cu,V)-12(n-1)n; n = 3, 4]. The samples were grain aligned under a high magnetic field of 7T. Two kinds of magnetic hysteresis data, one with the magnetic field parallel to the c-axis (DeltaM(parallel to)) and the other with the magnetic field perpendicular to the c-axis (DeltaM(perpendicular to)), were measured for the aligned samples. In both phases, the anisotropy factors R = (DeltaM(parallel to))/(DeltaM(perpendicular to)) ecrease to values, less than unity,with increasing temperature and increasing magnetic field, i.e., DeltaM(parallel to) < for a high temperature and/or high magnetic field region. Two sets of values were calculated for critical Current density and irreversibility field, corresponding to DeltaM(parallel to) and DeltaM(perpendicular to). Anisotropies of these properties are discussed in terms of vortex structures with the magnetic field parallel and perpendicular to the c-axis.