Magnetostrictive Properties of Galfenol Alloys Under Compressive Stress

TLDR

Fe–Ga alloys retain the α‑Fe structure and offer high‑strength, low‑cost magnetostrictive properties, with magnetostriction rising sharply when Fe is partially replaced by Ga, and exhibiting high saturation magnetization (~1.7 T) and Curie temperatures (~700 °C). The study aims to measure magnetostriction in Fe1−xGax alloys with 13–24 % Ga (Galfenol). Magnetostriction was measured on Fe1−xGax (x = 0.13–0.24) alloys under compressive stress to evaluate its dependence on composition. A 19 % Ga substitution produced a 12‑fold increase to ~400 ppm, with most alloys saturating below 24 kA/m even under >100 MPa compressive stress; near Fe3Ga (x = 0.24) magnetostriction peaked above room temperature, while small Ni and Mo additions reduced room‑temperature λ100.

Abstract

Fe–Ga alloys, in which the α-Fe structure is maintained, are rich sources of high strength, low cost magnetostrictive alloys for transducer and vibration reduction applications. Although the magnetostriction of Fe itself is very low, when a relatively small fraction of the Fe atoms are replaced by Ga, the magnetostriction, (3/2)λ100, increases greatly. Until recently, the highest magnetostriction was found with the replacement of Fe by Al (Alfenol). In this paper, we present our measurements of magnetostriction on Fe1−xGax, 0.13≤x≤0.24, (Galfenol). With the substitution of 19% Ga for Fe in Fe1−xGax, a 12-fold increase in magnetostriction to ∼ 400 ppm occurs, even though Ga is non-magnetic. In these alloys, the saturation magnetizations remain high, Ms≅1.7 T, and the Curie temperatures are far above room temperature, TC≅700°C. In most alloys studied, the magnetostrictions and magnetizations are fully saturated in fields less than 24 kA/m, even under compressive stresses >100 MPa. For x=0.24 (near Fe3Ga), an anomalous increase in magnetostriction with temperature occurs with a peak magnetostriction above room temperature. Small additions of Ni and Mo to the binary Fe–Ga alloys decrease the room temperature value of λ100.