Structurally heterogeneous model of extrinsic magnetostriction for Fe-Ga and similar magnetic alloys: Part II. Giant magnetostriction and elastic softening

A compositionally and structurally heterogeneous model for decomposing ferromagnetic alloys was developed in Part I of this article, and applied to Fe-Ga alloys. Here, we show that the giant extrinsic magnetostriction and elastic softening of these alloys can be caused by the macroscopic strain generated by a magnetic-field-induced confined displacive transformation or a stress-induced reorientation of tetragonal phase microdomains that form due to this underlying compositional heterogeneity. The exchange mechanism of the microdomain reorientation under an applied magnetic field is considered. A possibility of other mechanisms, associated with dislocations in the bee solution or antiphase boundaries in the DO3 ordered phase, are also discussed. The observed magnetomechanic and elastic softening are consistent with the predictions of the model.