CRITICAL CURRENTS AND FLUX-CREEP IN VANADIUM-DOPED YBA2CU3O7-DELTA SYSTEM

Vanadium (V) doped for Cu-site in YBa2Cu3O7-delta samples prepared by ceramic technique have been characterised by a.c.susceptibility techni que and d.c.magnetisation measurements. Detailed magnetisation measure ments on randomly oriented powdered sample of YBa2(Cu0.98V0.02)307-del ta as a function of temperature and field exhibit pronounced M(H) hyst eresis loops indicative of large flux pinning even as T approaches T(c ). It is believed that,the flux pinning arises due to the preferential substitution of V on Cu(2)-site, which acts as a pinning centre.The c ritical current density, J(c), deduced from the M(H) data at 10K, vari es from 10 10(5) A/cm2 to 5.5 10(5) A/cm2 in the field from 4 KOe to 1 2 KOe respectively, which is nearly seven times larger than the J(c) o f the pristine 1-2-3 powdered sample. The behaviour of J(c) in the mag netic fields is explained in terms of the flux creep model.