MAGNETISM IN BCC FE-AL ALLOY

The magnetic moment mu, hyperfine field B-hf and isomer shift IS at th e Fe site in bcc Fe-Al alloys were calculated from first principle. Co ntrary to the belief that Al atoms reside in the iron lattice as magne tic holes, it was found that the local magnetic moment of Fe is decrea sed when Al is at a nearest neighbour site (NN), while it increases if Al is at a next-nearest neighbour site (NNN). Consequently, the avera ge mu per Fe atom was found to be, initially, independent of Al conten t. Assuming a linear dependence of mu(Fe), on the number of Al atoms a t NN and NNN sites, we calculated the average mu, which was found to a gree with experimental results of cold worked alloys for disordered Fe -Al alloy. On the other hand, antiferromagnetic coupling appears in th e CsCl ordered structures. The average B-hf was also calculated and co mpared to experimental data and the trends in the IS are considered.