Microstructure and $J_{\rm C}$ Characteristics of Er123 Films With Artificial Pinning Centers

Abstract

Critical current density and surface resistance are evaluated for dilute Zn substituted high quality ErBa2Cu3O7-zeta films. Dilute Zn substituted ErBa2Cu3O7-zeta films are grown on SrTiO3 substrates by a pulsed laser deposition technique. Targets used in the experiments are un-substituted, 0.3at. %, 0.5at.%, 1.0at.% and 10at.% Zn substituted ErBa2Cu3O7-zeta ceramics. Crystal structures, field angular dependence of critical current density and surface resistance are evaluated. Zn substituting into YBa2Cu3O7-zeta has been studied for understanding the origin of oxide superconductivity with substituting level of several %. In this study, dilute Zn below 1.0 at.% is mainly adopted. Further substitution reduces its critical temperature. We intended to introduce zero-dimensional superconductivity killer atoms into CuO2 plane as artificial pinning centers. The obtained Zn substituted ErBa2Cu3O7-zeta films are c-axis oriented without peaks from other phases. The sharp drop temperature of surface resistance decreases as the Zn substitution. However, the surface resistance at a low temperature around 20 K is almost the same among the ErBa2Cu3O7-zeta films with different Zn substitution. We also measured the field angular dependence of critical current density of the Zn substituted ErBa2Cu3O7-zeta films. There are no strong angular dependences. Dilute zinc substitution increases critical current density for almost of all directions. However, in a high magnetic field of several tesla, pinning force around the field direction of a-axis is enhanced. Double introduction of one dimensional artificial pinning centers such as BaZrO3 nano-rods and zero dimensional artificial pinning centers is thought to be very effective for increasing critical current density for power cable applications.