Role of Nd/Ba Disorder on the Penetration Depth of Nd{sub 1+x}Ba{sub 2-x}Cu{sub 3}O{sub 7-{delta}} Thin Films

We report on a study on the effect of Nd/Ba disorder on the ab -plane penetration depth of epitaxial Nd{sub 1+x}Ba {sub 2-x}Cu{sub 3}O{sub 7-{delta}} thin films. While in stoichiometric samples {lambda}(T) at low temperature is linear, Nd-rich films exhibit a quadratic law. For low Nd excess (x 0.15) the data are explained if Nd/Ba disorder becomes less effective as a source of scattering. The effect of localization has been discussed to account for the experimental results. (c) 2000 The American Physical Society.