Neutron study of local environment effects and magnetic clustering inFe0.7Al0.3

Abstract

Ordered ${\mathrm{Fe}}_{0.7}$ ${\mathrm{Al}}_{0.3}$ is ferromagnetic below 400 K but becomes paramagnetic on cooling below 170 K and then is mictomagnetic below 92 K. We have used neutron-scattering methods to probe the microscopic magnetic-moment distribution of this alloy. Diffuse scattering data show the presence of large ferromagnetic clusters throughout all of these ordered regions and that the bulk behavior results from intercluster coupling. The Bragg scattering data yield Fe moments for the different lattice sites that are consistent with, and provide refined moment values for, a previously suggested local environment model. The results are interpreted in terms of clustered regions of $\alpha$-site Fe atoms with $n\ge 4$ and $n<\mathrm{}4\mathrm{}$ Fe nearest neighbors.