(1 Tohoku Univ., 2 ESICMM-NIMS, 3 Daido Steel Co. Ltd.)
Abstract:
Hot-deformed Nd-Fe-B magnets are not only high-performance magnets but also very good specimens for the study on magnetization reversal process due to their microstructure of well-aligned platelet grains and the high c-axis orientation. In this study, we have discussed the magnetization reversal process of the hot-deformed Nd-Fe-B magnets through the magnetic viscosity and the first-order reversal curve (FORC) analyses. Recently we developed the new analytical method of magnetization reversal process based on the magnetic viscosity measurements [1]. We have employed this method for differently processed hot-deformed Nd-Fe-B magnets which exhibit different coercivities. Irrespective of the values of coercivity and the measured temperature, their magnetization reversal processes are assigned as domain wall depinning with a very small energy barrier. This fact indicates that the domain wall depinning process in the hot-deformed magnet is triggered by a very small nucleus with the size of nanometer scale. The FORC diagram analysis has been widely adopted for various kinds of magnetic samples including sintered Nd-Fe-B magnets. However, it is difficult to understand the FORC diagrams of sintered Nd-Fe-B magnets due to their very complicated patterns. On the other hand, we have found that the FORC diagrams of the hot-deformed Nd-Fe-B magnets are well described by the Preisach model [2]. By using rod shape samples with small demagnetization factors, the FORC diagram analysis reveals that the hot-deformed Nd-Fe-B magnets have very small distributions of coercivity and interaction field. This result would be strongly related to the magnetization reversal process as discussed above.
This work is partially supported by the ESICMM and the Management Expenses Grants for National Universities Corporations from MEXT.
This work is partially supported by the ESICMM and the Management Expenses Grants for National Universities Corporations from MEXT.
[1] S. Okamoto et al., J. Appl. Phys. 118, 223903 (2015).
[2] T. Yomogita et al., REPM 2016 Proceedings, 249 (2016).
[2] T. Yomogita et al., REPM 2016 Proceedings, 249 (2016).
Related Links:
