Ab initio search for a high permeability material based on bcc iron

Using the fully relativistic spin-polarized Korringa-Kohn-Rostoker method, we study the prototypical soft magnet, bcc iron. We investigate how its magnetic anisotropy (MAE) varies as a function of volume, band filling, and tetragonal distortions of the crystal lattice. We follow the trends of the linear magnetostriction and magnetic permeability. We find that a slight reduction in band filling and modest lattice expansion produces a significant magnetic softening of this model system. We explore whether this situation can be realized by doping bcc Fe with vanadium. Treating the compositional disorder with the coherent potential approximation, we calculate the magnetic anisotropy and magnetostriction trends of iron-rich ${\mathrm{Fe}}_{1\ensuremath{-}c}{\mathrm{V}}_{c}$ disordered alloys and find the behavior to accord with the predictions from the bcc Fe model. In particular we find that for $c\ensuremath{\approx}0.1$ the MAE is very small and the linear magnetostriction is zero. We propose ${\mathrm{Fe}}_{0.9}{\mathrm{V}}_{0.1}$ as a high permeability material. Fair agreement with experimental values for the MAE and magnetostriction of both Fe and FeV is found.