Critical current characteristics of YBa2Cu3O7 thin films on (110) SrTiO3

The material and electrical characteristics of YBa2Cu3O7 (YBCO) thin Rims d eposited by inverted cylindrical magnetron sputtering on (110) SrTiO3 (STO) were investigated. X-ray diffractometry shows the grain orientations to be predominantly the YBCO (110) and (103) with no evidence of c-axis grains. Electron micrographs show the film surface to consist of coupled elongated grains parallel to the (110) STO edge. The films were patterned into small 2.5 mm squares parallel to the substrate edges for electrical characterizat ion. Transport currents parallel and perpendicular to the (110) substrate e dge showed a 945:1 anisotropy in film resistance and a factor of two in cri tical current density for temperatures below 60% of the transition temperat ure (T-c), The temperature dependence of the critical current near T-c was quadratic-like and strongly dependent on the value of T-c used in the analy sis. For the two orientations, there was nearly a 6K difference in T-c as d etermined by the point at which the critical current became zero. The respo nse of the critical current to small magnetic fields was greater for transp ort current along the c-axis direction and was observable over a temperatur e interval nearly four times greater than for current along the basal plain . These YBCO thin films have good response to small magnetic fields and are suitable for vortex flow device development. Index Terms-High-temperature superconductors, microwave measurements, superconducting films, superconduc ting materials, superconducting materials measurements.