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

We investigated the application of Nd 2 Fe 17 N 3 magnetic powder with planar magnetic anisotropy to magnetic field amplification materials at several tens of MHz. 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 air. In this study, microstructural analysis conducted using transmission electron microscopy and X-ray diffraction revealed that the coating layer became thicker, and the Nd 2 Fe 17 N 3 surface was phase-separated into nano-sized α-Fe phases and Nd-rich phases, either oxide, oxynitride, or nitride. Additionally, the nano-sized α-Fe phases and the nano-sized Nd-rich phases were oriented over a wide area spanning several hundred nanometers. We concluded that these characteristic structures have led to improved properties.