FLUX PINNING MECHANISM OF HIGH-TC Y-BA-CU-O SUPERCONDUCTOR CONTAINING ARTIFICIAL PINNING CENTERS Y2BACUO5

Magnetic field and temperature dependences of magnetic torque and magnetic relaxation were investigated on Y-Ba-Cu-O superconducting systems containing Y2BaCuO5 artificial particulate precipitates. Two different types of pinning forces were found to act on fluxoids. One is the intrinsic pinning force due to a layered structure of Cu-O planes and the other is the extrinsic pinning force due to Y2BaCuO5 precipitates. The intrinsic pinning force is effective when the applied magnetic field is lying within an angle DELTAtheta out of the Cu-O planes. The pinning potential obtained from the magnetic relaxation measurements is expressed by the form of log (J(c)/j) where j is the shielding current density. The pinning mechanism is discussed in terms of the planar pinning at the precipitates and the transformation of fluxoid lines from stepwise to linear.