FLUX-PINNING AND CRITICAL CURRENTS BY MO-SUBSTITUTION IN YBA2CU3O7-DELTA

Mo-substituted samples with stoichiometric composition YBa2(Cu1-xMox)( 3)O-7-delta, where 0 < x < 0.04, prepared under identical conditions h ave been characterized by d.c. magnetization and thermogravimetric ana lysis measurements. D.C. magnetization measurements on randomly orient ed powdered systems, as a function of temperature and field, exhibit a n M(H) hysteresis loop, indicative of moderate flux pinning even as T approaches T-c. We feel that this flux pinning arises due to the prefe rential substitution of Mo on the Cu-site, which acts as a pinning cen tre. Intragrain critical current density, J(c), values deduced from ma gnetization measurements for x=0.01-0.04 at H=5 kOe and T=15 K decreas e with increasing Mo concentration due to decreasing free carrier conc entration, p.