Europhys. Lett., 52 (2), p. 210 (2000)

Vortex clustering: The origin of the second peak in the
magnetisation loops of type-two superconductors

D. K. Jackson ¹ - M. Nicodemi ¹ - G. K. Perkins ² -
N. A. Lindop ³ - H. Jeldtoft Jensen ¹

 ¹ Department of Mathematics, Imperial College
Queen's gate 180, London SW7 2BZ, UK
 ² Blackett Laboratory, Imperial College - Prince Consort Road, London SW7 2BZ, UK
 ³ Department of Chemistry, University of Edinburgh - Edinburgh EH9 3JJ, UK

PACS :
74.60.Ge - Flux pinning, flux creep, and flux-line lattice dynamics
74.60.-w - Type-II superconductivity
74.25.Ha - Magnetic properties

h.jensen@ic.ac.uk

Abstract:

We study vortex clustering in type-II superconductors. We demonstrate that the "second peak'' observed in magnetisation loops may be a dynamical effect associated with a density-driven instability of the vortex system. At the microscopic level the instability shows up as the clustering of individual vortices at (rare) preferential regions of the pinning potential. In the limit of quasi-static ramping the instability is related to a phase transition in the equilibrium vortex system.

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