First-principles investigation of the effect of substitution and surface adsorption on magnetostrictive properties of Fe-Ga alloys

TL;DR

This study uses density functional theory to explore how substitutional elements and surface adsorption influence the magnetostrictive properties of Fe-Ga alloys, aiming to optimize their performance for practical device applications.

Contribution

It demonstrates that small substitutional additions can significantly enhance magnetostriction, and surface treatments can tune grain alignment for improved properties.

Findings

Substituting 1.6% of elements like Ag, Pd, Cu can double magnetostriction.

Surface adsorption of active atoms affects surface energy and grain orientation.

Proper surface treatments are necessary for optimal magnetostrictive performance.

Abstract

Materials with large magnetostriction are widely used in sensors, actuators, micro electromechanical systems, and energy-harvesters. Binary Fe-Ga alloys (Galfenol) are the most promising rare-earth-free candidates combining numerous advantages such as low saturation magnetic field (~200 Oe), excellent ductility and low cost, while further improving their performance is imperative for practical applications. Using density functional theory calculation, we report results of the effect of substituting small amount of additional elements X (eg. X = Ag, Pd and Cu) on magnetostriction of Fe-Ga alloys, and find that it may double the magnetostriction with a substitutional percentage of only 1.6%. Moreover, adsorbents with high chemical activity (eg. O or Os atoms) may affect the surface energy of different face-orientations of Fe-Ga alloys, indicating proper surface treatments are necessary to tune the alignment of Fe-Ga grains to achieve better performance. These results may be helpful to further optimize the magnetostrictive properties of Fe-Ga alloys for device applications.