Flux pinning in thin films of YBa2Cu3O7-x

Thin films of YBa2Cu3O7-x are deposited on MgO substrates via dc magnetron sputter technic. The thicknesses varry between 10nm and 500nm. The films are patterned by dry etching method. Narrow stripes with widths down to 1 μm are obtained without serious degradation, e.g. Tcoff > 85K and Tc < 1.5K. The critical properties of the bridges are determined by resistive measurements. The upper critical field, Bc2(T), and the irreversibility line, Tc2*(T), are derived from the resistive transition in fields up to 14 Tesla and from extrapolation of the pinning data, respectively. The volume flux-pinning force Fp=Jc.B is measured as a function of temperature, and applied magnetic induction. A strong increase of the critical current density with decreasing width of the bridges was found. A discussion of the flux pinning data in the context of the flux-line shear model is given. (orig.)