Volume magnetostriction of Fe₈₁(Ga_1-xGe _x)₁₉ alloys

Linear and volume magnetostrictions were investigated in the as-cast Fe81 Ga19 and Ge doped Fe81 (Ga1-x Gex) 19 (x=0.1, 0.2, and 0.3) alloys by measuring the change in length along the three-dimensional directions of the samples. For as-cast Fe81 Ga19 alloy, when the applied field was lower than about 0.3 T, the linear magnetostriction was positive along the direction of the field, but became negative in another two orthogonal directions normal to the applied field. Volume expansion was observed along all the three directions at the applied field over 0.3 T. Due to the contribution of the volume expansion, namely, volume magnetostriction, the longitudinal magnetostriction increased from 27 ppm at 0.3 T to 47 ppm at 2.0 T. The saturation of volume magnetostriction was absent at 2 T and should be higher with further increasing field. Not only the linear magnetostriction but also the volume magnetostriction can be drastically enhanced by doping Ga in Fe. The same phenomena were observed in Fe81 (Ga1-x Gex) 19 alloys. The as-cast Fe81 Ga19 alloy exhibits mainly a disordered bcc A2 phase, and the Ge doped Fe81 Ga19 alloys keep the A2 structure with a smaller lattice constant.