Electronic structure and magnetic properties of the metastable \(\hbox {Au}_{1-x}\hbox {Fe}_{x}\) alloy films

Abstract

A set of the metastable at room temperature (RT) \(\hbox {Au}_{1-x}\hbox {Fe}_{x}\) alloy films (\(0.01\le \hbox {x}\le 0.98\)) were fabricated using DC RT magnetron co-sputtering of Au and Fe targets. It was shown that the solid solution of Fe in face-centered cubic (FCC) Au is formed in \(\hbox {Au}_{1-x}\hbox {Fe}_{x}\) alloy films for \(0.01\le \hbox {x}\le 0.77\). At \(x\approx 0.80\), the transition from the FCC type to body-centered cubic (BCC)-type ordered \(\hbox {Au}_{1-x}\hbox {Fe}_{x}\) alloy films takes place. The first-principle calculations of the density of electronic states, the cohesive energies, and element resolved magnetic moments (\(m_{Au}\) and \(m_{Fe}\)) have been performed for FCC-type ordered structures \(\hbox {L1}_{2}\)-\(\hbox {Au}_{0.75}\hbox {Fe}_{0.25}\), \(\hbox {L1}_{0}\)-\(\hbox {Au}_{0.50}\hbox {Fe}_{0.50}\), and \(\hbox {L1}_{2}\)-\(\hbox {Au}_{0.25}\hbox {Fe}_{0.75}\). The calculations reveal that among these alloys, the \(\hbox {Au}_{0.25}\hbox {Fe}_{0.75}\) is the most stable as having the largest cohesive energy. It was also shown that both Au and Fe atoms contribute to the calculated resulting magnetic moment \(M_{AuFe}\) of \(\hbox {Au}_{1-x}\hbox {Fe}_{x}\) alloys but have an opposite compositional dependence on Fe content. The general decrease in calculated magnetic moment of \(\hbox {Au}_{1-x}\hbox {Fe}_{x}\) alloys \(M_{AuFe}\) with a decrease in x nicely agrees with the experimentally determined compositional dependence of magnetic properties of \(\hbox {Au}_{1-x}\hbox {Fe}_{x}\) alloy films. Unlike the literature results, the experimentally determined M(x) dependence shows two different parts related to the films with FCC type or BCC type of structure.