On the scaling behaviour of cross-tie domain wall structures in patterned NiFe elements

¹  University of Glasgow, Department of Physics and Astronomy - Glasgow G12 8QQ, United Kingdom
²  Universität Bonn, Institute for Applied Mathematics - Wegelerstr. 10, 53115 Bonn, Germany

Received: 3 August 2007
Accepted: 9 October 2007

Abstract

The cross-tie domain wall structure in micrometre and sub-micrometre wide patterned elements of NiFe, and a thickness range of 30 to 70 nm, has been studied by Lorentz microscopy. Whilst the basic geometry of the cross-tie repeat units remains unchanged, their density increases when the cross-tie length is constrained to be smaller than the value associated with a continuous film. This occurs when element widths are sufficiently narrow or when the wall is forced to move close to an edge under the action of an applied field. To a very good approximation the cross-tie density scales with the inverse of the distance between the main wall and the element edge. The experiments show that in confined structures, the wall constantly modifies its form and that the need to generate, and subsequently annihilate, extra vortexanti-vortex pairs constitutes an additional source of hysteresis.