Competing anisotropies and temperature dependence of exchange bias in [formula omitted] metallic wire arrays fabricated by nanoimprint lithography

Abstract

The magnetic behavior of exchange biased [formula omitted] bilayer metallic wire arrays, fabricated by nanoimprint lithography, was studied and compared with identical thin film heterostructures. A significant uniaxial shape anisotropy, [formula omitted], in addition to the unidirectional exchange anisotropy, [formula omitted], and the intrinsic uniaxial anisotropy, [formula omitted] observed in the unpatterned film, was introduced in the wire arrays through wire patterning. The competing anisotropies were shown to modify the angular dependence of exchange bias, [formula omitted], and coercivity, [formula omitted], for wire arrays. In addition, an asymmetric behavior is observed for both wire arrays and unpatterned film and is attributed to the noncollinear alignment of uniaxial and unidirectional anisotropies. Temperature dependence of [formula omitted] is different for the wire arrays from the unpatterned thin film. This and the large deviation from ideal cubic anisotropy in the antiferromagnet for the wire arrays are both in agreement with Malozemoff's model of exchange bias. © 2010, American Institute of Physics. All rights reserved.