Magnetic Microstructures of 2:17 Type Sm(Co, Fe, Cu, Zr)z Magnets Detected by Magnetic Force Microscopy

The magnetic microstructures of 2:17 type Sm(Co, Fe, Cu, Zr)z magnets were detected by magnetic force microscopy. Comparing the microstructures of the specimens coated with and without Ta thin film before and after heat-treatment, it is found that: (a) as a protection layer, Ta coating layer about 20 nm thick can effectively restrain Sm volatilization under high temperature; (b) the stress built in the 2:17 type Sm-Co magnets during specimen preparation only affects some local parts of the domain structures; (c) the magnetic microstructures vary largely for specimens heat-treated at high temperature without Ta film coating due to Sm volatilization. In addition, by comparing with high coercivity Fe-Pt point tips, it is found that the Co-Cr thin-film tips are not suitable for detecting the magnetic microstructures of strong permanent magnets.