Out-of-plane magnetic anisotropy in ordered ensembles of FeyN nanocrystals embedded in GaN

Abstract

Phase-separated semiconductors containing magnetic nanostructures are relevant systems for the realization of high-density recording media. Here, the controlled strain engineering of GadFeN layers with FeyN embedded nanocrystals (NCs) via AlxGa1-xN buffers with different Al concentration 0 < xAl < 41% is presented. Through the addition of Al to the buffer, the formation of predominantly prolate-shaped ε-Fe3N NCs takes place. Already at an Al concentration xAl ≈ 5% the structural properties-phase, shape, orientation-as well as the spatial distribution of the embedded NCs are modified in comparison to those grown on a GaN buffer. Although the magnetic easy axis of the cubic γ'-GayFe4-yN nanocrystals in the layer on the xAl = 0% buffer lies in-plane, the easy axis of the ε-Fe3N NCs in all samples with AlxGa1-xN buffers coincides with the [0001] growth direction, leading to a sizeable out-of-plane magnetic anisotropy and opening wide perspectives for perpendicular recording based on nitride-based magnetic nanocrystals.