Microstructure of Nd2Fe17N3 Magnetic Powder Surface With Nano-α-Fe Phases Separated Surface Layer

We investigated the application of Nd2Fe17N3 magnetic powder with planar magnetic anisotropy to magnetic field amplification materials at several tens of megahertz. Consequently, we succeeded in developing a magnetic property with real permeability ~8 and imaginary permeability below 0.8 at 100 MHz using a phosphoric acid coating and a simple heat treatment process in the air. In this study, microstructural analysis conducted using transmission electron microscopy (TEM) and X-ray diffraction (XRD) revealed that the coating layer became thicker, and the Nd2Fe17N3 surface was phase-separated into nano-sized <inline-formula> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula>-Fe phases and Nd-rich phases, either oxide, oxynitride, or nitride. In addition, the nano-sized <inline-formula> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula>-Fe phases and the nano-sized Nd-rich phases were oriented over a wide area spanning several hundred nm. We concluded that these characteristic structures have led to improved properties.