Bulk electron states with Δ symmetry in disordered Fe-based alloys for magnetic tunnel junctions

Using first principles methods, we have calculated the changes in the density of states (DOS) with Delta(1) and Delta(5) symmetry, induced by alloying effects in Fe1-xVx, Fe1-xCrx, and Fe1-xCox disordered body centered cubic (bcc) alloys. The Fe1-xVx and Fe1-xCrx disordered alloys behave similarly, with Delta(1) Bloch states which remain 100% spin-polarized over the whole range of concentrations. Alloying effects have different consequences in Fe1-xCox alloys for which the minority spin Delta(1)-DOS becomes finite at intermediate concentrations. Results on the Delta(5)-DOS are also given as a function of the composition for the three bcc alloys. The alloying effects mainly affect the minority spin channel for Fe1-xCox alloys and the majority spin channel for Fe1-xVx and Fe1-xCrx alloys. These results could be useful for the interpretation of magnetotransport experiments in magnetic tunnel junctions with a MgO(001) barrier and bcc Fe-based alloy electrodes.