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

Abstract

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 (SRO) 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 slowcooled 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 any) effect on the enhanced magnetostriction. However, the dramatic suppression of magnetostriction near ∼20 at. % Ga can be linked rapid growth of SRO just before the onset of long-range chemical order. 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 slowcooled 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 magnetostriction near ϳ20 at. % Ga can be linked rapid growth of SRO just before the onset of long-range chemical order.

Structure and properties of high damping Fe-Ga based alloy

“…1. This conclusion is in agreement with the results of the transmission synchrotron X-ray study [25], where short range B2 ordering was reported.…”

Experimental exploration of the origin of magnetostriction in single crystalline iron

“…25,26 Short-range order ͑SRO͒, thought to be a precipitation precursor of long range chemically ordered precipitate, has little effect on the magnetostriction. 27 Together, these experimental results suggest the origin of magnetostriction in these alloys is intrinsic. The sensitivity of DiffXAS to a small strain as demonstrated in this work shows that this technique can be applied to single crystals of Fe-X single crystals in probing the neighboring atomic pairs that show largest and smallest strain.…”

Investigation on the structural and magnetic properties of sputtered TbFe2/Fe3Ga heterostructures

“…Finally, our samples are sputtered films that are as-grown and annealed at low temperatures, and so they might have a different microstructure than the bulk crystalline high-temperature annealed samples studied in previous works. [2][3][4][5][6][7]18,19 Taking into account all of these aspects, we can indicate that our experimental results point to a cubic structure in the Fe 3 Ga layers, being not observed evidences of the D0 3 phase.…”

“…Advanced characterization techniques have been used to analyze the strong correlation between the microstructure and the magnetoelastic properties in this material system. [2][3][4][5][6][7] These studies have proved that it is essential to precisely control the structural ordering in order to achieve a magnetostriction constant (k) of around 400 ppm in crystalline and 280 ppm in polycrystalline bulk Galfenol samples. 8,9 These high magnetostriction constants are achieved in quenched samples with Ga contents of 19% and 28%.…”