Edge saturation fields and dynamic edge modes in ideal and nonideal magnetic film edges

Abstract

This paper describes modeling of the micromagnetic behavior near edges of ferromagnetic thin films when uniform fields are applied in plane and perpendicular to the edge. For ideal film edges with vertical edge surfaces, the field required to saturate the magnetization perpendicular to the edge, ${H}_{\mathrm{sat}}$, and the frequency of precession in the localized edge mode are calculated using numerical micromagnetics for a wide range of film thicknesses. Analysis of the critical state at the saturation field and the full micromagnetic results are used to develop a simple macrospin model for the edge magnetization. This model predicts both ${H}_{\mathrm{sat}}$ and edge mode precession frequency values that agree well with the micromagnetic results. Three classes of nonideal edges are also modeled: tilted edge surfaces, diluted magnetization near the edge, and surface anisotropy on the edge surface. Despite their different physical mechanisms, all three of these defects produce similar reductions in ${H}_{\mathrm{sat}}$ and similar dynamic properties of the edge magnetization.