Critical-current measurements have been made on sputtered Nb-Ta multilayers for both perpendicular and parallel applied field. For large bilayer periods, the pinning force behaves as h(1-h) and is due to dislocation pinning. As the bilayer period decreases, the pinning force decreases and changes over to a collective mechanism. For parallel applied field, there is a lack of temperature scaling and an increase in the pinning force, which is due to pinning by the multilayering. A search for the existence of other effects is discussed.

• Received 7 August 1987

DOI:https://doi.org/10.1103/PhysRevB.37.68