Quantitative atomic order characterization of a Mn2FeAl Heusler epitaxial thin film

Abstract

<jats:title>Abstract</jats:title> <jats:p>In this work, we investigate the effect of anti-site disorder on the half-metallic properties of a Mn<jats:sub>2</jats:sub>FeAl Heusler alloy thin film. The film was grown on TiN-buffered MgO 001 substrates via magnetron sputtering. A detailed structural characterization using x-ray diffraction (XRD) and anomalous XRD showed that the film crystallizes in the partially disordered <jats:italic>L</jats:italic>2<jats:sub>1</jats:sub> <jats:italic>B</jats:italic> structure with 33% disorder between the Mn(B) and Al(D) sites. We measure a positive anisotropic magnetoresistance in the film, which is an indication of non-half metallic behaviour. Our x-ray magnetic circular dichroism sum rules analysis shows that Mn carries the magnetic moment in the film, with a positive Fe moment. Experimentally determined moments correspond most closely with those found by density functional calculated for the <jats:italic>L</jats:italic>2<jats:sub>1</jats:sub> <jats:italic>B</jats:italic> structure with Mn(B) and Al(D) site disorder, matching the experimental structural analysis. We thus attribute the deviation from half-metallic behaviour to the formation of the <jats:italic>L</jats:italic>2<jats:sub>1</jats:sub> <jats:italic>B</jats:italic> structure. To realize a half-metallic Mn<jats:sub>2</jats:sub>FeAl film it is important that the inverse Heusler <jats:italic>XA</jats:italic> structure is stabilized with minimal anti-site atomic disorder.</jats:p>