Effect of site disorder on the electronic properties of Fe2VAl Heusler alloy

Ab initio calculations on ordered L21 structure of Fe2VAl alloy have been carried out by introducing B2, DO3, A2′ and XY-XZ type disorders in order to understand the role of anti-site disorder on magnetic and transport properties. These studies show an enhancement of individual spin moments of anti-site Fe atoms in DO3, A2′ and XY-XZ type anti-site disorder, making the Fe2VAl alloy magnetically active. These calculations also show that hybridization due to covalent distribution of valance states among the atoms is important in Fe2VAl, defining its unusual physical properties. From the density of states spectrum obtained near the Fermi level, we have noticed formation of intermediate defect-like states that couple the edges of the pseudo gap on both sides of the Fermi level, driving the material from semi-metallic to metallic type in electrical transport. We also present experimental results on structural, magnetic and electrical properties of Fe2VAl Heusler alloy. A comparison of present experimental data with calculations shows an existence of DO3 type anti-site disorder due to the Al-deficiency in Fe2VAl alloy which causes deviations in theoretical results on the magnetic and transport behaviour of pure Fe2VAl. The temperature dependence of electrical transport and magnetic data analysed on the basis of impurity band model which provides convincing evidence for itinerant character of this alloy system with an anti-site disorder.