Magnetism in bcc Fe-Al alloy

The magnetic moment Μ, hyperfine field B_hf and isomer shift IS at the Fe site in bcc Fe-Al alloys were calculated from first principle. Contrary to the belief that Al atoms reside in the iron lattice as magnetic holes, it was found that the local magnetic moment of Fe is decreased when Al is at a nearest neighbour site (NN), while it increases if Al is at a next-nearest neighbour site (NNN). Consequently, the average Μ per Fe atom was found to be, initially, independent of Al content. Assuming a linear dependence of Μ_Fe on the number of Al atoms at NN and NNN sites, we calculated the average Μ, which was found to agree with experimental results of cold worked alloys for disordered Fe-Al alloy. On the other hand, antiferromagnetic coupling appears in the CsCl ordered structures. The average B_hf was also calculated and compared to experimental data and the trends in the IS are considered.