Effect of laser irradiation on the superconducting properties of high-T_c SmBa₂Cu₃O_x

Abstract

Studies of the effect of high power laser (Q-switched Ruby laser, 694 nm, 30 ns) irradiation on the critical current density (J_c ) and magnetic hysteresis at 77K and temperature variation of microwave induced d.c. voltage on SmBa₂Cu₃O_x ceramic samples have been performed. Irradiation did not substantially change T_c but caused a strong increase in J_c and magnetic hysteresis at 77K. The microwave-induced d.c. voltage at 77K showed appreciable decrease after irradiation. SEM studies showed grain growth due to sintering which improves the interconnectivity among the superconducting grains. These are attributed to physical densification and consequent reduction in the number of weak links. The increase of magnetic hysteresis after laser irradiation is presumably connected with the creation of defects which act as pinning centres. Thermal modelling suggests that on irradiation the surface melts up to a depth of 1μ and laser-induced evaporation occurs at energy density of 2.5 J/cm².