Dimensional crossovers in collective flux pinning

Abstract

The pinning force density in ribbons of melt spun (a) Zr70Cu30 is found to obey the Larkin-Ovchinnikov theory of collective pinning by dislocation loops, and shows two and three dimensional behaviour, besides an intermediate regime not contemplated by the theory. The dimensional crossovers allow determination of the radius of action of the pinning forces which is shown to be proportional to the coherence length. Its magnitude is too small, which points to quantitative shortcomings of the current theory.