Numerical investigation of domain walls in constrained geometries

Abstract

In recent years, magnetic domain wall structures in ferromagnetic nanowires have attracted growing attention, opening paths to develop novel devices which exploit magnetoresistive effects. A reduction of the domain wall length in geometrically constrained areas has been predicted and observed. In this article, we consider a rectangular constriction (width s₀, length 2d₀) in form of a thin film, attached to a rectangular pad (width s1) on either side. The material considered is Ni (M_s = 490 kA/m) with a weak in-plane anisotropy (K₁ = 2000 J/m³). We investigate the dependence of the domain wall length as a function of the constriction geometry. Micromagnetic simulations are used to systematically study the head-to-head domain walls between head-to-head domains (case A) and N´eel walls between sidewise domain orientations (case B). We present the resulting domain wall length w as a function of 2d₀ and s₀ and analyze the magnetization patterns. A reduction of the domain wall length to below 11nm is found (where the corresponding unconstrained domain wall length is 69nm). For constriction lengths above a critical value (case B only), the single 180 domain wall splits into two 90 domain walls.

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Identifiers

ORCID for Richard P. Boardman: orcid.org/0000-0002-4008-0098

ORCID for Cornelis H. de Groot: orcid.org/0000-0002-3850-7101

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