Dc magnetic properties of Mn doped YBa2Cu3O7-delta superconductor

Dc magnetization measurements were carried out on YBa2(Cu1-xMnx)3O(7-delta) samples with x taking values 0, 0.01, 0.015, 0.02, 0.025, 0.035 and 0.05, YBa2(Cu0.975Fe0.025)3O(7-delta), YBa2(CU0.975Ni0.025)(3)O7-delta and YBa2(C u0.975Zn0.025)(3)O7-delta samples up to a maximum field of 5 T at temperatu res 5, 50 and 77 K. The effect of Mn on the zero field critical current den sity, J(cg)(0), estimated from the remnant magnetization, in general, is a monotonic suppression up to a concentration of 2.5% Mn and shows a saturati on beyond that concentration. The field and temperature dependences of 2.5% Mn doped YBa2Cu3O7-delta samples were better than those of the Ni, Fe and Zn at the same doping level. Anomalous increases in J(cg) (0), the indicati ve lower criticalfield, H-c1g*, and the bulk flux pinning force, F-p, obser ved in the 2.0% Mn doped sample, at 50 and 77 K, have been attributed to th e matching of the Abrikosov vortex density generated over these temperature s and the defect induced number of pinning sites due to the Mn doping.