Enhanced damping capacity of ferromagnetic Fe-Ga alloys by introducing structural defects

The irreversible motion of magnetic domain walls in ferromagnets can dissipate a large portion of the elastic energy, and the associated damping capacity is proportional to the magnetostriction constant. In contrast, here we found that the damping capacity of the large magnetostriction Fe-Ga alloys can be enhanced by 2–3 times through introducing structural defects including interfacial dislocations and stacking faults, despite that these defects deteriorate the magnetostriction. These structural defects were introduced by aging the BCC (body-centered-cubic) solution-treated precursor, for which the formation of mechanically harder FCT (face-centered-tetragonal) and /or FCC (face-centered-cubic) phases can result in high-density partial dislocations at the semi-coherent phase interfaces and quasi-periodically stacked nano-layer substructure inside the FCC variants. The structural defects act as extra damping sources besides the magnetic domain walls because the structural accommodation of the semi-coherent phase interfaces between BCC and FCT/FCC nanoprecipitates with different elastic moduli and the nano-layer substructure towards long-range ordered periodical stacking can dissipate a large portion of mechanical energy. These findings suggest that introducing structural defects provides fresh freedom to design high damping ferromagnetic materials.