Cao Yongze, Zhao Yue, Tang Jin, Du Haifeng, Zhou Yan, Saito Hitoshi
Department of Physics, Dalian Maritime University, Dalian, 116026, China.
Regional Innovation Center, Akita University, Tegata Gakuen-machi 1-1, Akita, Japan.
Ultramicroscopy. 2020 May;212:112980. doi: 10.1016/j.ultramic.2020.112980. Epub 2020 Mar 16.
Probing the dynamic magnetic domain of permanent magnet materials under an external AC magnetic field using magnetic force microscopy is challenging as well as important to reveal their pinning sites and local magnetization processes. In this work, we develop alternating magnetic force microscopy (A-MFM) with a Co-GdO superparamagnetic tip for observing the dynamic magnetic domain wall (DW) motion in a, b plane Nd-Fe-B sintered magnets by stimulating the magnetization of the superparamagnetic tip and Nd-Fe-B sample using an external AC magnetic field. This method enables the simultaneous measurement of DC and AC magnetic fields from the sample surface. The measurement results reveal that the DW motion does not happen until the amplitude of the external AC magnetic field reached 77 Oe (zero to peak). Further increasing the external AC magnetic field strength leads to DW motion with larger movement area and stronger AC magnetic field originating from the DW motion. In addition, A-MFM images shows the pinning sites of the DW motion. The present work provides a direct and effective approach to studying the local dynamic magnetization processes of the magnetic materials on the nanometer scale.
利用磁力显微镜探测外部交流磁场下永磁材料的动态磁畴，对于揭示其钉扎位点和局部磁化过程而言，既具有挑战性又至关重要。在这项工作中，我们开发了一种带有Co-GdO超顺磁探针的交变磁力显微镜（A-MFM），通过使用外部交流磁场激发超顺磁探针和钕铁硼样品的磁化，来观察a、b平面钕铁硼烧结磁体中的动态磁畴壁（DW）运动。该方法能够同时测量样品表面的直流和交流磁场。测量结果表明，直到外部交流磁场的幅度达到77 Oe（从零到峰值）时，磁畴壁运动才会发生。进一步增加外部交流磁场强度会导致磁畴壁运动的运动面积更大，且源于磁畴壁运动的交流磁场更强。此外，A-MFM图像显示了磁畴壁运动的钉扎位点。本工作为在纳米尺度上研究磁性材料的局部动态磁化过程提供了一种直接有效的方法。
