An analytic study on coercivity mechanism of exchange coupled Nd2Fe14B/α-Fe nanocomposite magnets

In this study, a coercivity mechanism has been suggested for exchange coupled soft/hard nanocomposite magnets to estimate the coercive field from maximum domain wall energy gradient at the soft/hard phase grain boundary. A derivable function γ(x) has been suggested near the soft/hard grain boundary to reflect detailed microstructures (e.g. grain sizes of hard and soft phases) and the coercivity has been expressed by the first derivative dγ(x)/dx. Using the model, for exchange coupled Nd2Fe14B/α-Fe nanocomposite multilayer systems, relation between the coercivity and α-Fe layer thickness has been estimated and analyzed by comparing with the results from prior experimental and micromagnetic studies.