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Title: Special pinning phenomena in arrays of defects with gradient spatial distributions on niobium film

Flux pinning effect is related to the strong influence by the presence of defects that act as pinning centers. We present transport experiments that investigate the pinning properties in a spacing-graded array of pinning sites. We have found the asymmetric pinning by arrays of defects with modulated gradient spatial distributions on niobium film. One can clearly see the asymmetric pinning effect for the vortex motion. The dc voltage depends on the amplitude of the ac current and that there is a sharp maximum at matching fields. This curve, however, has an interesting sign reversal phenomenon below the first matching field, which will be investigated more in the future. The dc voltage as a function of dc and ac applied current gives evidence that the artificial arrays of gradient pinning site density induce ratchet effect. This effect can be used to control the vortex motion, which will be important for the application of vortex based on electronic devices.
Authors:
 [1] ; ;  [2]
  1. Department of Electronic Engineering, National Formosa University, Yunlin, Taiwan (China)
  2. Department of Physics, National Changhua University of Education, Changhua, Taiwan (China)
Publication Date:
OSTI Identifier:
22409928
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 17; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ALTERNATING CURRENT; ASYMMETRY; CONTROL; CRYSTAL DEFECTS; DIAGRAMS; DIRECT CURRENT; ELECTRIC POTENTIAL; FILMS; MAGNETIC FIELD REVERSAL; MAGNETIC FIELDS; MAGNETIC FLUX; NIOBIUM; SPATIAL DISTRIBUTION