Structure, magnetostrictive, and magnetic properties of heat-treated Mn₄₂Fe₅₈ alloys

The newly discovered large magnetostriction in antiferromagnetic γ-Mn-Fe alloy is of interest to develop a new kind of ductile and low-cost magnetostrictive materials. This work presents a detailed study on the structures, magnetostrictive, and magnetic properties of a heat-treated Mn₄₂Fe₅₈ alloy by X-ray diffraction (XRD), transmission electronic microscopy (TEM), and superconducting quantum interference device (SQUID) magnetometer. The single γ-phase separates into a mixture containing a face-centered-cubic (fcc) γ-phase, a hexagonal close-packed (hcp) ε-phase, and a body-centered-cubic (bcc) α-phase after isothermal heat treatment for 24 h at 1100 °C. Such phase separation in Mn₄₂Fe₅₈ alloy not only leads to a slight increase in lattice parameter a of the γ-phase and Néel temperature T_N, but also results in an obvious enhancement in magnetization due to the presence of ferromagnetic bcc phase. The magnetostrictive performance, however, deteriorates accompanying with the phase separation.