Temperature and field direction dependences of first-order reversalcurve (FORC) diagrams of hot-deformed Nd-Fe-B magnets

First-order reversal curve (FORC) diagram has been previously adopted for the analyses ofmagnetizationreversal process and/or quantitative evaluation of coercivity and interaction field dispersionsin variousmagnetic samples. Although these kinds of information are valuable for permanent magnets,previouslyreported FORC diagrams of sintered Nd-Fe-B magnets exhibit very complicated patterns. Inthis paper, wehave studied the FORC diagrams of hot-deformed Nd-Fe-B magnets under various conditions.Contrary tothe previous reports on sintered Nd-Fe-B magnets, the FORC diagram of the hot-deformedNd-Fe-B magnet exhibits a very simple pattern consisting of a strong spot and a weak line.From this FORC diagrampattern, it is revealed that the coercivity dispersion of the hot-deformed Nd-Fe-B magnets issurprisinglysmall. Moreover, this feature of the FORC diagram pattern is very robust and unaffected bychanges invarious conditions such as grain boundary diffusion process, temperature, and field direction,whereasthese conditions significantly change the coercivity and the shape of magnetization curve. Thisfact indicates that the magnetization reversal process of the hot-deformed Nd-Fe-B magnetsis almost unchangedagainst these conditions.

This work was supported by the Elements Strategy Initiative Project under the auspice of MEXT andthe Management Expenses Grants for National Universities Corporations from MEXT.