Magnetostriction of iron-germanium single crystals

The addition of nonmagnetic Ga into body-centered cubic Fe enhances the magnetostriction constant λ100 over tenfold. Literature reports for substitution of Ge at low concentrations suggest that the addition of Ge also enhances the magnetostriction. In this work, the magnetostriction and microstructure of Fe–Ge were investigated to correlate magnetostriction with microstructure. The magnetostriction of Fe100−xGexsingle crystals with x between 0.05 and 0.18 varies with Ge concentration and correlates with phase changes. The value of (3/2)λ100 increases with Ge additions in the A2 single phase region (up to x ∼ 10), reaching a maximum of 94 ppm at the solubility limit of the disordered A2 phase. Further increases in Ge in the A2+D03 two-phase region (12\u3cx\u3c16)result in a decrease in magnetostriction which changes from positive to negative. For Ge contents with x\u3e16, magnetostriction remains negative with an absolute value of strain of129 ppm at 18 at. % Ge. This behavior is similar to that observed for Fe–Si alloys