Direct observation of magnetization in Nd-Fe-B permanent magnets by transmission electron microscopy

초록

Direct observation of magnetization in Nd-Fe-B permanent magnets by transmission electron microscopy Hyun Soon Park Department of Materials Science and Engineering, Dong-A University Among the permanent magnets currently available, sintered Nd2Fe14B magnets show the best magnetic properties (Ku ~ 4.5 MJ m-3, Hc ~ 1.1 MA/m, ?0Ms ~ 1.6 T); that is, they show the largest value of maximum-energy product [(BH)max > 400 kJm-3]. Since the large maximum energy product leads to a remarkable degree of miniaturization of motors and actuators, these magnets can significantly contribute to power saving and/or green technologies. In fact, Nd?Fe?B magnets have been applied in traction motors of hybrid electric vehicles, and as actuators of hard disk drives. In order to further improve both coercivity (Hc) and maximum-energy product (BH)max, understanding the magnetization process and the magnetism at the ultrathin grain boundary (GB) region is of vital importance. In this talk, using in situ Lorentz TEM and electron holography, I present the observations of magnetization reversal and the magnetism at the ultrathin GB region in a thin film of sintered Nd2Fe14B [1,2]. [1] H. S. Park, et.al, J. Appl. Phys. 97, 033908 (2005). [2] Y. Murakami, et.al, Acta. Mater. 71, 370 (2014).