Large-magnetostriction ternary alloys obtained from Galfenol through partial substitution of Ga

In this paper the magnetoelastic characteristics of ternary Fe–Ga–X (X=Ge, Sn) alloys are compared with those of Galfenol (Fe–Ga) within the same range of solute concentration. New magnetostriction and elastic modulus data for Fe–Ga–Ge at six different compositions are presented. The most notable case is that of Fe86.9Ga9.9Ge8.7. Although the tetragonal magnetostriction, λ100, of Fe–Ge is lower overall than that of Fe–Ga, the magnetostriction of the aforementioned ternary alloy equals the value of Galfenol at the same solute concentration, Fe86.9Ga13.1. The theory proposed for explaining the measured λ100 values in the ternary alloys takes into account the total number of electrons each solute contributes to the alloy. The valence of Fe is taken to be “1” from first-principles calculations. Previously published results on Fe–Ga–Sn [Summers et al., “Magnetostriction of binary and ternary Fe-Ga alloys,” J. Mater. Sci 42, 9582–9594 (2007)] concur with this theory (Sn and Ge belong to the same periodic table group). The Sn ternary alloys are of economic importance for large-scale applications given that significant magnetostriction can be achieved while using less expensive solutes. It is also notable that, when compared with Galfenol at a Ga concentration of x=6.2 at. %, the ternary alloy Fe88.1Ga6.2Ge5.7 has a magnetostriction that is larger by a factor of 2.