Observation of microstructures and magnetic domains of Sm-Co based permanent magnets by high-voltage electron microscopy

Abstract

Microstructures and magnetic domains of precipitation hardened Sm(Co0.653Fe0.257Cu0.066Zr 0.024)7.3 permanent magnets were investigated using a high-voltage electron microscope. The cellular microstructures controlled by step aging were clearly observed on atomic scale by high-voltage HREM. It was found that the cell interior phases of as-sintered magnets contained microtwins but those of step aged magnets contained the Z phase on the basal plane with disappearance of the twins. Also, Lorentz electron microscope images showed that the domain wall pinning at the cell boundary phases of the SmCo5 structure was increased by the step aging. Furthermore, the intensity distributions of Lorentz electron microscope images obtained by imaging plates were compared with the calculated intensity distribution, and the domain wall width was evaluated to be 10 nm.