Magnetostriction and crystal structure of Fe-M (M = Ga, Al, Ge, V, Ni, Co, Si) polycrystalline alloys

Our research investigates a variable magnetic flux motor that utilizes magnetostrictive materials where the relative permeability changes in response to the stress induced by centrifugal force. To realize this concept, development of materials with high magnetostriction is essential. We prepared materials exhibiting large magnetostriction using iron-based binary alloys and investigated their underlying magnetostrictive mechanisms. Alloy ingots with nominal compositions of Fe100−xMx (x = 0 to 20; M = Si, Al, Ge, Ga, Ni, Co, and V) were prepared by arc melting. High magnetostriction was obtained in Fe80Ga20 (58 ppm) and Fe80Al20 (47 ppm). The magnetostriction of iron alloys is determined by the balance between the repulsive force from the anisotropy of the electron density distribution on the 3d electron orbital (corresponding to coercivity Hc) and the attractive force from the metallic bonding strength among iron atoms (corresponding to the lattice constant a).