Thickness evolution of coercivity in ultrathin magnetic films

TL;DR

This paper presents a theoretical model analyzing how ultrathin magnetic film coercivity evolves with thickness, considering surface roughness and anisotropy effects, revealing key dependencies on film geometry and step anisotropy.

Contribution

It introduces a model incorporating surface roughness and step anisotropy to explain coercivity evolution in ultrathin magnetic films, extending previous theories.

Findings

Coercivity depends on film thickness and top layer coverage.

Sample geometry and step anisotropy size influence coercivity.

Magnetostatic interactions modify results quantitatively but not qualitatively.

Abstract

The thickness evolution of in-plane magnetization reversal in ultrathin films is studied with a theoretical model that takes account of surface roughness typical of epitaxial growth. Guided by N\'{e}el's model, step edge sites of monolayer-height islands are assigned a two-fold anisotropy in addition to a four-fold anisotropy at all sites. Coercivity is found to depend essentially on both the film thickness and the partial coverage of the topmost layer. Its qualitative features are determined primarily by sample geometry and the size of the step anisotropy compared to the domain wall energy. Magnetostatic interactions change the results quantitatively, but not qualitatively. Their effect is understood by comparing calculations with and without their inclusion.