Correlation between microstructure and first-order magnetization reversal in the SmCo5/α-Fe nanocomposite magnets

SmCo5/α-Fe nanocomposite magnets with different morphology have been fabricated by ball milling of the micrometer sized SmCo5 and α-Fe powders. The α-Fe grains vary from elongated nano-strips to spherical nanoparticles with increasing milling time. The inter-phase exchange coupling is enhanced with increasing milling time due to reduced grain size. The first-order reversal curves (FORCs) are taken to identify optimal conditions for exchange coupling. It has been found that the stripped morphology results in weak inter-phase exchange coupling, while enhanced exchange coupling is observed with further reduction of the soft-phase grain size. Compared with the measurement of demagnetization curves, FORC analysis provides more information on the magnetostatic as well as the exchange interactions.