High-Frequency Magnetic Properties of Nd2Fe17N3 Magnetic Powders with Nano-α-Fe Phase-Separated Surface Layers

In this study, Nd 2 Fe 17 N 3 powder was coated with transition metals and rare-earth phosphate layers. Subsequently, the phosphate layers were phase separated into outer Fe 2 O 3 and inner Nd 2 O 3 layers via heat treatment in air. Simultaneously, the phase-separated layers of nanosized α-Fe and rare-earth-rich phases were formed at the interface between the Nd 2 Fe 17 N 3 and phosphate layers. The resulting powder was classified into particle sizes of 20-38 μm and molded into a toroidal core shape. Then, its magnetic properties were measured in the megahertz range. The real permeability (μʹ) and loss tangent (tanδ) at 10 MHz were approximately 11.19 and 0.02, respectively. The treated powder exhibited a two-fold enhancement and 10-fold reduction in the values of μʹ and tanδ, respectively, in relation to the untreated Nd 2 Fe 17 N 3 powder. The developed treatment protocols can be used to synthesize magnetic powders with magnetic coupling and insulating properties, which can facilitate the development of megahertz-range magnetic cores.