Issue Europhys. Lett. Volume 58, Number 4, May 2002 Page(s) 582 - 588 Section Condensed matter: electronic structure, electrical, magnetic, and optical properties DOI 10.1209/epl/i2002-00435-1

DOI: 10.1209/epl/i2002-00435-1


Europhys. Lett., 58 (4) , pp. 582-588 (2002)

Magnetic-force microscopy of vortices in thin niobium films: Correlation between the vortex distribution and the thickness-dependent film morphology

A. Volodin¹, K. Temst¹, C. Van Haesendonck¹, Y. Bruynseraede¹, M. I. Montero² and I. K. Schuller<sup>2

1</sup>  Laboratorium voor Vaste-Stoffysica en Magnetisme, Katholieke Universiteit Leuven Celestijnenlaan 200 D, B-3001 Leuven, Belgium
²  Department of Physics, University of California-San Diego La Jolla, CA 92093-0319, USA

(Received 5 June 2001; accepted in final form 15 February 2002)

Abstract
We demonstrate the possibility to reliably image vortices in superconducting Nb films with a low-temperature magnetic-force microscope. Our force microscope enables to monitor the surface topography as well, allowing to correlate the location of the vortices with specific topographic features. For Nb films of different thickness ( ) and different ( ) we studied how the vortex configuration changes when changing the applied magnetic field under field-cooled conditions ( ). We find that the vortex pinning preferentially occurs in between the grains appearing at the film surface. This is consistent with a distribution of pinning centers which is governed by the columnar growth of the Nb films. For thicker Nb films the vortex arrangement is no longer dominated by pinning alone, and there appear short-range correlations in the vortex lattice. The short-range correlations are enhanced when increasing the applied magnetic field.

PACS
74.60.Ge - Flux pinning, flux creep, and flux-line lattice dynamics.
68.37.Rt - Magnetic force microscopy (MFM).
74.76.Db - Conventional superconducting films.


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