Positive in-plane and negative out-of-plane magnetoresistance in the overdoped high-temperature superconductor Bi2Sr2CaCu2O8+x

The in-plane and out-of-plane magnetoresistances of moderately overdoped Bi2Sr2CaCu2O8+x Single crystals have been studied, from T-c+5 K to T-c+100 K with the magnetic field oriented :perpendicular and parallel to the current, respectively. The in-plane magnetoresistance is positive, the out-of-plane magnetoresistance negative, and their temperature variations depend on the orientation of the magnetic field. A recent theory for superconducting order parameter fluctuations is extended for the interaction of carrier spins with the magnetic field. The anomalous, anisotropic magnetoresistance can be described well by a unique set of physical parameters, which were found to correspond to estimates from the normal-state transport properties. [S0163-1829(99)08317-4].