Enhancing the limit of uniaxial magnetic anisotropy induced by ion beam erosion

Abstract

Artificial tailoring of magnetic anisotropy by manipulating interfacial morphology and film structure is of fundamental interest from an application point of view in spintronic and magnetic memory devices. This Letter reports an approach to engineer and enhance the strength of oblique incidence ion beam erosion (IBE)-induced in-plane uniaxial magnetic anisotropy (UMA) by simultaneous modification of film morphology and film texture. Cobalt film and Si substrate have been taken as a model system to meet this objective. Unlike conventional thin film deposition on ripple patterned substrate or post-growth IBE of film, we direct our effort to the sequential deposition and subsequent IBE of the film. Detailed in situ investigation shows that the film grows in a textured polycrystalline state with the formation of nanometric surface ripples. The film also exhibits pronounced UMA with an easy axis oriented parallel to the surface ripple direction. Remarkably, the induced UMA is about one order of magnitude larger than the IBE-induced UMA reported earlier. The capability of imposing in-plane crystallographic texture throughout the film layer gives rise to magneto-crystalline anisotropy along with the shape anisotropy of nanometric surface ripples, which enhances the strength of the UMA and illustrates the universal applicability of the present method.