Relation between Ga ordering and magnetostriction of Fe-Ga alloys studied by x-ray diffuse scattering

Transmission synchrotron diffraction was employed to characterize the Ga ordering in magnetostrictive Fe 100−x Ga x alloys with Ga concentrations from 0 to 20.3 at. %. The experiments focused on the development of atomic short-range ordering ͑SRO͒ by analysis of the diffuse scattering appearing at superlattice positions of the D0 3 ordered alloy structure. No SRO was found for Ga concentrations less than 4 at. %. Between 13 and 20.3 at. %, D0 3-type SRO clusters are observed whose size increases with Ga concentration for both slow-cooled and quenched samples. Thermal quenching of the samples suppresses the cluster sizes when compared to slow-cooled samples of the same concentration. For quenched samples with large Ga concentration, Ga pairing is evidenced by growing B2-type correlations. At low concentrations, the presence of SRO appears to have little ͑if any͒ effect on the enhanced magnetostriction. However, the dramatic suppression of magneto-striction near ϳ20 at. % Ga can be linked rapid growth of SRO just before the onset of long-range chemical order.