Magnetization reversal of (Sm, Ce)₂(Co, Fe, Cu, Zr)₁₇magnets as per soft x-ray magnetic circular dichroism microscopy

We investigated magnetization reversal of (Sm, Ce)2(Co, Fe, Cu, Zr)17 magnets as per x-ray magnetic circular dichroism microscopy. Magnetization reversal initially occurs at the ferromagnetic grain boundaries or in the vicinity of nonmagnetic Sm oxides. As the demagnetization field increases after magnetization reversal, the reversal region extends into the grain from these areas by the magnetic domain wall motion. Energy-dispersive x-ray analysis using an electron probe micro-analyzer shows that, at the grain boundaries, the Fe concentration is higher and the Cu concentration is lower compared to that inside of the grains; and concentrations of Sm, Co, Fe, and Cu vary in the vicinity of Sm oxides. By measuring the Co L3 absorption intensity, we verified that local coercivities in these areas are very low compared to those inside of the grain. These results imply that the magnetization reversal that occurs in these areas is induced by the variation in the composition. The results obtained in our research will be useful for improving the magnetic properties of Sm-Co magnets.