The investigation of magnetostriction of different phases in Fe-Co alloys

Magnetostrictive material is an important magnetic functional material and can be applied in many fields such as micro-sensors and micro-actuators ^[1-3]. Among magnetostrictive materials, non-rare-earth Fe-based alloys have gained great interest due to their high mechanical strength, good ductility, large magnetostriction at low saturation fields, high imposed-stress levels, and relatively low cost ^[4]. However, there were few reports about relation of magnetostriction and phase structure. In this paper, a series of Fe_100-xCo_x alloys was synthesized in different phase components. The largest magnetostriction was achieved in Fe₂₅Co₇₅ which was the composition near the morphotropic-phase boundaries (MPB). In addition, Fe₂₀Co₈₀ alloys with the b.c.c and f.c.c pure phase were separately synthesized by different preparation methods. It was found that its b.c.c phase showed a negative magnetostriction, while f.c.c phase had a positive magnetostriction. The magnetostriction behaviors were explained for the Fe-Co alloys with different phases.