Experimental and theoretical evidences that atomic disorder suppresses half-metallicity of Heusler compounds

Abstract

Half-metallic compounds present two spin bands with contrasting behaviors, resulting in 100% of spin polarization at the Fermi level; property of crucial importance for applications in spintronic devices. Materials presenting this characteristic are, for instance, some Heusler compounds, mainly Co2-based compounds, which have interesting properties, such as TC above 1000 K and high values of saturation magnetization. However, atomic disorder can affect the half-metallic properties of these materials, decreasing their potential application in spintronic devices. Our aim is to evaluate the role played by atomic disorder in Co2FeSi, which has a Curie temperature of 1100 K and saturation magnetization close to 6 μB. In order to experimentally probe the effects of atomic disorder in this material, samples were subjected to different annealing times, with a subsequent quantification of the disorder degree by means of anomalous X-ray diffraction (AXRD) and Mössbauer spectroscopy. In addition, DFT calculations were performed to provide information on the density of states (DoS) at the Fermi energy under those disorder conditions. This work reveals how disorder plays an important role on the thermodynamic and electronic properties of half-metallic Heusler compounds.