Chen Xinfeng, Higashikozono Soma, Ito Keita, Jin Lei, Ho Ping-Luen, Yu Chu-Ping, Tai Nyan-Hwa, Mayer Joachim, Dunin-Borkowski Rafal E, Suemasu Takashi, Zhong Xiaoyan
National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE), The State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China.
Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan.
Ultramicroscopy. 2019 Aug;203:37-43. doi: 10.1016/j.ultramic.2019.02.016. Epub 2019 Feb 19.
Metastable α″-FeN thin films were reported to have a giant saturation magnetization of above 2200 emu/cm in 1972 and have been considered as candidates for next-generation rare-earth-free permanent magnetic materials. However, their magnetic properties have not been confirmed unequivocally. As a result of the limited spatial resolution of most magnetic characterization techniques, it is challenging to measure the saturation magnetization of the α″-FeN phase, as it is often mixed with the parent α'-FeN phase in thin films. Here, we use electron energy-loss magnetic chiral dichroism (EMCD), aberration-corrected transmission electron microscopy, X-ray diffraction and macroscopic magnetic measurements to study α″-FeN (containing ordered N atoms) and α'-FeN (containing disordered N atoms). The ratio of saturation magnetization in α″-FeN to that in α'-FeN is determined to be 1.31 ± 0.10 from quantitative EMCD measurements and dynamical diffraction calculations, confirming the giant saturation magnetization of α″-FeN. Crystallographic information is also obtained about the two phases, which are mixed on the nanoscale.
1972年有报道称亚稳α″-FeN薄膜具有高于2200 emu/cm³的巨大饱和磁化强度，并被视为下一代无稀土永磁材料的候选者。然而，它们的磁性能尚未得到明确证实。由于大多数磁表征技术的空间分辨率有限，测量α″-FeN相的饱和磁化强度具有挑战性，因为它在薄膜中常与母相α'-FeN相混合。在此，我们使用电子能量损失磁圆二色性（EMCD）、像差校正透射电子显微镜、X射线衍射和宏观磁测量来研究α″-FeN（含有序N原子）和α'-FeN（含无序N原子）。通过定量EMCD测量和动态衍射计算，确定α″-FeN与α'-FeN的饱和磁化强度之比为1.31±0.10，证实了α″-FeN的巨大饱和磁化强度。还获得了关于这两个在纳米尺度上混合的相的晶体学信息。
