Direct determination of local exchange stiffness in M-type ferrites via domain-wall analysis with tilt-scan-averaged DPC STEM

Exchange stiffness is a fundamental micromagnetic parameter, yet its value in hard ferrites has remained uncertain due to the limitations of traditional thin-film spin-wave experiments. In this work, the authors utilize tilt-scan-averaged differential phase-contrast STEM to directly measure ${180}^{\ensuremath{\circ}}$ domain-wall widths in Sr-based and Ca-La-Co-based M-type ferrites. By combining these real-space measurements with bulk anisotropy constants, the authors quantify local exchange stiffness with high precision. This approach reveals that variations in domain-wall width are driven by magnetocrystalline anisotropy rather than changes in exchange stiffness, providing a powerful new tool for mapping magnetic properties at the nanoscale within complex microstructures.