ANGULAR-DEPENDENCE OF THE DISORDER CROSSOVER IN THE VORTEX LATTICE OFBI2.15SR1.85CACU2O8+DELTA BY MUON SPIN ROTATION AND TORQUE MAGNETOMETRY

Using the techniques of muon spin rotation and torque magnetometry, we investigate the crossover field B-cr in Bi2.15Sr1.85Ca1Cu2O8+delta at which the vortex lattice becomes disordered along the field direction . It is found that B-cr scales as the projection of the applied field along the perpendicular to the superconducting planes. This has the im plication that a field large enough to give a disordered lattice when applied perpendicular to the planes, can give a well-ordered vortex-li ne lattice for angles of the field to the c axis greater than a critic al value.