Enhanced magnetoelastic stress in disordered iron–gallium alloy thin films revealed by direct measurement
Year: 2025
Type: article
Abstract: The large magnetostriction in FeGa alloys is relevant for manifold applications, but for thin films, it can play a prominent role in controlling the strength of the magnetic anisotropy. Bulk samples show values depending on the extensive preparation procedure compendium, which is limited in its temperature range for high-quality thin-film synthesis. Here, we present a study of the magnetoelastic coupling coefficients B 1 and B 2 in epitaxial FeGa thin films below 50 nm deposited on the MgO(001) surface at 150 °C by the cantilever method. Series of films with 22, 28, and 33 at. % Ga do not show thickness-dependent variations for B 1 and B 2 , but − B 1 for the 22 at. % Ga composition is 10 MPa, roughly 2 times the bulk value and smaller than the bulk-like value of − B 1 =12.1 MPa obtained for a film with 17 at. % Ga. This enhancement is correlated with the A2 crystal structure for the film rather than the coexistence with D0 3 or other ordered nanometric precipitates proposed for bulk samples. Synchrotron diffraction excludes the formation of long-range L6 0 , or D0 3 precipitates in samples with (001)A2 peaks at concentrations around 25 at. % Ga, which implies partial chemical disorder. The analysis of extended x-ray absorption fine structure measurements points to a D0 3 local order with a residual number of Ga-Ga pairs. Considering that the substrate quenches the movable strain in the A2 phase described in dual-phase structures, our results point to the important role of the electronic structure of the iron atoms modified by the presence of Ga in the alloy. This effect enlarges B 1 in films with the A2 phase, stabilized using epitaxial growth.
Source: Journal of Alloys and Compounds
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,660
OpenAlex ID: W4411329621