Magnetostriction of ternary Fe-Ga-X (X = C, V, Cr, Mn, Co, Rh) alloys

Binary iron-gallium (Galfenol) alloys have large magnetostrictions over a wide temperature range. Single crystal measurements show that additions of 2 at. % or greater of 3d and 4d transition elements with fewer (V, Cr, Mo, Mn) and more (Co, Ni, Rh) valence electrons than Fe, all reduce the saturation magnetostriction. Kawamiya and Adachi [J. Magn. Magn. Mater. 31-34, 145 (1983)] reported that the D0(3) structure is stabilized by 3d transition elements with electron/atom ratios both less than iron and greater than iron. If D0(3) ordering decreases the magnetostriction, the maximum magnetostriction should be largest for the (more disordered) binary Fe-Ga alloys as observed. Notably, addition of small amounts of C (0.07, 0.08, and 0.14 at. %) increases the magnetostriction of the slow cooled binary alloy to values comparable to the rapidly quenched alloy. We assume that small atom (C, B, N) additions enter interstitially and inhibit ordering, thus maximizing the magnetostriction without quenching.