Microstructure and hard magnetic properties of nanocomposite Sm2Fe15Ga2Cx permanent magnets with an excess of Fe prepared directly by melt spinning

Abstract

The nanocomposites Sm–Fe–Ga–C with low Sm contents have been prepared directly by melt spinning without a subsequent heat treatment. A highly isotropic remanence to saturation magnetization ratio of 0.6–0.7 and a relatively high coercivity of 5.5 kOe were achieved from the as-quenched ribbons. X-ray diffraction and thermomagnetic analyses show that the as-quenched ribbons consist of a magnetically hard phase Sm2Fe15Ga2Cx and a magnetically soft phase α-Fe. Transmission electron microscopy observation demonstrates that the major 2:17-type phase has larger crystallites and the crystallites of the minor phase α-Fe are smaller and located separately at the grain boundaries of the major phase. The remanence enhancement is attributed to the exchange coupling between the intergrains. Both microstructure and magnetic properties are found to depend sensitively on the substrate velocity. The effect of the microstructure on hard magnetic properties has been discussed.