A specific model for domain-wall nucleation in thin-film Permalloy microelements (invited)

Abstract

A particular mechanism for domain-wall nucleation in thin (350 Å) Permalloy films of typical geometry (7×140 μm) used for magnetoresistive (MR) sensors is studied in detail. A numerical micromagnetic model is described which can theoretically predict an observed domain-wall process (including domain-wall creation, destruction, and intermediate wall motions and magnetization distributions) without imposition of prior assumptions concerning domain-wall existence or artificial nucleation mechanisms. Calculated results for the nucleation and annihilation fields of a parallel pair of Néel domain walls responsible for observed Barkhausen noise in an MR sensor yield good overall agreement with experimental magnetoresistive measurements. An analysis of the energetics of the wall nucleation/annihilation process is provided. Bitter pattern measurements confirming the proposed domain-wall mechanism are also included.