Intergranular interaction in nanocrystalline Ce-Fe-B melt-spinning ribbons via first-order reversal curve analysis

First-order reversal curve (FORC) diagram, which visualizes the variation of magnetic interaction on a field plane, has been applied to nanocrystalline Ce-Fe-B melt-spinning ribbons. The FORC diagram exhibits different vertical spread along the Hu axis when the applied field is parallel or perpendicular to the ribbon surface. The discrepancy of vertical spread corresponds to different intergranular interactions, which can also be verified by Henkel plot, another method to identify the interactions. The larger vertical spread on the Hu axis along the perpendicular direction is ascribed to the dominance of magnetostatic interaction, while the smaller one along the parallel direction indicates the existence of stronger exchange coupling interaction. The remanence enhancement effect along the parallel direction further confirms the existence of exchange coupling. These indicate that a FORC diagram is a powerful evaluation method for distinguishing different magnetic interactions in permanent magnets. Moreover, Lorentz transmission electron microscopy was used to analyze the magnetic domain structure of nanocrystalline Ce-Fe-B melt-spinning ribbons.