Characteristics of flux pinning in (formula presented) superlattices

The resistivity of (Formula presented) (Formula presented) superlattices under magnetic fields was measured to investigate the flux pinning and anisotropic superconducting properties, where n is the number of the modulation layer. The fields applied were parallel to the ab plane and the c axis of the films. The resistivity under magnetic fields shows thermally activated behavior. A power law magnetic field dependence of (Formula presented) in YBCO/PBCO superlattices was observed. The (Formula presented) was observed to scale to a constant which increases linearly when the thickness of YBCO layers is increased and decreases linearly when the thickness of PBCO layers is increased. There exists both one-unit-cell YBCO and interlayer YBCO couplings in YBCO/PBCO superlattices. These couplings affect the coherence lengths.