Magnetic properties of arrays of “holes” in Ni80Fe20films

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Abstract
We have studied the magnetization reversal and magnetoresistance behavior in lithographically defined structures based on a 400 Å Ni80Fe20 film. The structures consist of square arrays of holes with size d in the range from 0.5 to 15 μm fabricated using electron beam lithography and an optimized pattern transfer process. For the field applied along the intrinsic easy axis, a marked increase in the coercive field is observed as the hole size is decreased. This has been attributed to the pinning of the domain walls in the vicinity of the holes. However, for the field applied along the intrinsic hard axis direction, there is a marked increase in the remanence as the hole size is reduced due to the competition between the intrinsic uniaxial anisotropy field and the shape induced magnetic anisotropy field. Unusual magnetoresistance effects are observed as a function of orientation of applied field in submicron structures.