Critical current density and magnetic properties of a melt-processed Y _0.8Ho_0.2Ba₂Cu₃O_y superconductor

We have prepared a bulk Y_0.8Ho_0.2Ba ₂Cu₃O_y superconductor by the powder melting process method and investigated its magnetization curves and magnetic relaxation in the temperature range 55-77 K at different fields. The J_c values at a certain temperature and field is estimated by Bean's model. It is found that J_c decreases with the magnetic field according to a power law, whereas it drops exponentially with temperature. The dependence on temperature of the maximum diamagnetization field H_p and the remanent magnetization M_rem is discussed. The magnetic relaxation indicates that the magnetization M varies logarithmically with time. The relaxation rate dM/d ln t is also studied.