Abstract:
Variation of magnetic critical current density (J(mc)) and transport critical current density (J(tc)) in high magnetic fields at liquid helium temperature were investigated on Sm-Ba-Cu-O:Ag(x) (x = 0.0, 0.2, 0.4, and 0.6) superconducting samples prepared by the coprecipitation technique. T(c) and crystallographic parameters remain unaffected by Ag addition. However, both J(mc) and J(tc) were found to increase on Ag addition. The volume pinning force (F(p)) also increased with increase in Ag concentration, resulting in stronger flux line sheer. Microwave-induced d.c. voltage measurement shows a significant reduction of the total number of weak links between the superconducting grains with increasing concentration of Ag, which creates stronger pinning potentials between the boundary of the superconducting intergrains. Hence, the volume pinning force is greatly enhanced by Ag addition, leading to flux line lattice movement which is responsible for high J(mc) and J(tc).