In-situ observation of magnetization reversal process of Sm(Co,Cu,Fe,Zr)z magnets with different Fe contents

Sm(Co,Cu,Fe,Zr)(z) magnets have drawn much attention for high-temperature applications due to their high Curie temperature, strong corrosion resistance and thermal stability. The effect of increasing Fe content on the distribution of elements and squareness (S-r) of demagnetization curves were investigated for two kinds of magnets with different nominal compositions of Sm(CobalFe0.15Cu0.07Zr0.03)(7.8) and Sm(CobalFe0.28Cu0.07Zr0.03)(6.6) in this work. The magnetic properties of the magnets with higher Fe content fluctuate greatly after different solution treatments, indicating that they are more sensitive to the process temperature. The increase in Fe content can obviously enhance the cellular phase size. Meanwhile, inhomogeneous Cu distribution is observed in the Sm(CobalFe0.28Cu0.07Zr0.03)(6.6) magnet, resulting in the different cellular structures and corresponding magnetic domain patterns in different regions in the inner grains. Furthermore, the lower Cu content regions are responsible for the wider magnetic domain, which have weaker resistance to applied magnetic field. As a result, S-r of demagnetization curve decreases with the increase in Fe content due to the inhomogeneous Cu distribution, which was confirmed by in-situ observation of electron probe micro-analyzer (EPMA) and magneto-optical Kerr optical microscope (MOKE).