Superconducting properties of oriented YBa2Cu3O7-x films on MgO and SrTiO3 substrates

Using single-target sputter deposition, the c-axis oriented YBa2Cu3O7-x films can be obtained on both MgO and SrTiO3 substrates by appropriately controlling the substrate temperature at 700 C. However, on examining a.c. susceptibility and electrical dissipation, we find that the films on a SrTiO3 substrate possess better superconducting properties, such as a stronger coupling between the superconducting grains; a higher potential energy for flux pinning; and a larger capacity for current conduction. Also, from the magnetization hysteresis measurement, the critical current density of 2.6x106 A cm-2 (77K) and 4.5x107 A cm-2 (5 K) for the sample on the SrTiO3 substrate can be estimated. (orig.)