Novel angular scaling of vortex phase transitions in Bi2Sr2CaCu2O8+y

Local magnetization measurements using micro-Hall probes in Bi2Sr2CaCu2O8+y single crystals under various field angles 0 from the c axis reveal that t he angular dependence of the first order transition (H-FOT) and the second peak (H-p) is clearly different from the conventional scaling law. Instead, we found a novel angular scaling, which is expressed as HFOT, H-p proporti onal to [cos theta + alpha(T) sin theta](-1) [alpha(T): temperature depende nt parameter] in a wide angle range. Two possible origins for this novel an gular dependence are discussed: (1) The Effect of the electromagnetic coupl ing between pancake vortices and (2) the suppression of the Josephson coupl ing by the in-plane field. [S0031-9007(99)09180-2].