Effects of magnetic field heat treatment on Sm-Co/α-Fe nanocomposite permanent magnetic materials prepared by high energy ball milling

Effects of magnetic field heat treatment on the structure and magnetic properties of Sm-Co/α-Fe nanocomposite permanent magnetic materials fabricated by high energy ball milling are investigated in the present work. After a magnetic field heat treatment below 700 °C on as-milled amorphous Sm-Co/α-Fe samples, the nanocomposite magnets with strong hard and soft magnetic interaction, showing a hysteresis loop of single phase characteristic, are obtained. The coercivity increases with the increase of annealing temperature. The coercivity, remanence and remanence ratio of the Sm-Co/Fe nanocomposite magnets are all enhanced after a heat treatment at a magnetic field as compared with those of nanocomposite magnets heat treated without a magnetic field. X ray diffraction analysis shows that the diffusion between the Sm-Co hard and α-Fe soft phases is suppressed by the magnetic field applied during the heat treatment process, leading to the inhibition of the grain growth of nanocrystal Sm-Co and α-Fe phases, and a finer nanostructure is obtained. Thus, a higher coercivity, remanence and remanence ratio are realized in Sm-Co/α-Fe nanocomposite magnets after the magnetic field heat treatment. Magnetic field heat treatment also makes the direction of c axis of Sm-Co hard grains along the heat treatment magnetic field direction, leading to an enhancement of magnetic anisotropy of the Sm-Co/Fe nanocomposite magnets.