Effect of the Structural Disorder and Short-Range Order on the Electronic Structure and Magnetic Properties of the Fe2VAl Heusler Alloy

Resumo

The Fe₂VAl Heusler alloy is of great interest because ab initio calculations predict the absence of magnetization in it and a half-metal behavior with a pseudogap at the Fermi level. At the same time, experimental data (low-temperature specific heat, electrical resistivity, and magnetic properties) show that it is difficult to achieve such characteristics, and Fe₂VAl samples usually have the characteristics of a poor magnetic metal. Ab initio calculations have been performed for ordered and disordered (Fe_1–xV_x)₃Al Heusler alloys with x = 0.33. It has been shown that the alloy in a structurally ordered state (L2₁ structure) is a half-metal with a deep pseudogap at the Fermi level and does not have magnetization. At the same time, antisite defects in the iron and vanadium sublattices of the disordered alloy (D0₃ structure) lead to an increase in the conductivity and to the appearance of spin polarization and magnetization of (2.1±0.1)μ_B/f.u. The short-range order in the disordered phase has been generated by increasing the concentration of clusters characteristic of the bcc structure of α-Fe, which results in an increase in the magnetization to (2.5±0.1)μ_B/f.u.