Quantitative evaluation of local magnetic property using magnetic domain wall width measurement with tilt-scan averaged DPC STEM

Identifying the one-to-one relationship between microstructures and magnetic properties is crucial for improving the coercivity of permanent magnets. Magnetic domain wall (DW) is an important local magnetic structure, whose width is closely related to the local magnetic properties of the magnets. Unfortunately, due to the limitations of conventional experimental methods, direct and precise measurements of nanoscale DW widths have been challenging. However, recent advancements in differential phase contrast scanning transmission electron microscopy (DPC STEM) have enabled direct imaging of magnetic field distribution down to atomic dimensions. In this study, the precise measurement of the DW width in Nd-Fe-B type magnets using high-resolution DPC images in a magnetic field-free environment was demonstrated. The change in DW width with respect to the change in the magnet's local composition was measured. Moreover, we can estimate local magnetic properties such as exchange stiffness and magnetocrystalline anisotropy from the DW width. Therefore, DPC STEM can be used to evaluate the local magnetic properties of magnets with complex microstructures.