Magnetization measurements for grain boundary phases in Ga-doped
Journal of Alloys and Compounds vol.752 (2018)
新津甲大(理化学研究所),佐藤敦子(九州大学),佐々木泰祐(NIMS),澤田龍之介(九州大学),Cho Youngji(九州大学),高田幸生(豊田中央研究所),佐藤岳(豊田中央研究所),金子裕治(豊田中央研究所),加藤晃(トヨタ自動車),大久保忠勝(NIMS),進藤大輔(理化学研究所),宝野和博(NIMS), CA 村上恭和(九州大学) ( https://doi.org/10.1016/j.jallcom.2018.04.055 )
Abstract
The magnetism of grain boundary (GB) phases in the Nd-rich Ga-doped Nd-Fe-B sintered magnet that shows unusually high improvement in coercivity by post-sinter optimal heat treatment was studied using electron holography. Transmission electron microscopy observations identified three types of GB phases with distinct structures, i.e., Ia3-type, amorphous-type, and Nd6(Fe,Ga)14-type. The magnetic flux densities of these three GB phases were systematically analyzed by measuring the phase shifts of incident electrons, and all of these GB phases are concluded to be nonferromagnetic.
その他特記事項
This study was supported by JST, CREST, dedicated to the improvement of coercivity in Dy-free Nd-Fe-B permanent magnets. A part of the analysis using a large number of phase images was supported by another project of JST, CREST (JPMJCR1664), dedicated to the enhancement of sensitivity in electron holography. The authors are grateful to Dr. K. Harada, and Dr. T. Tanigaki for useful discussions about the electron holography observations.
