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

In this study, Nd2Fe17N3 powder was coated with transition metals and rare-earth phosphate layers. Subsequently, the phosphate layers were phase separated into outer Fe2O3 and inner Nd2O3 layers via heat treatment in the air. Simultaneously, the phase-separated layers of nanosized $\alpha $ -Fe and rare-earth-rich phases were formed at the interface between the Nd2Fe17N3 and phosphate layers. The resulting powder was classified into particle sizes of 20– $38 ~\mu \text{m}$ and molded into a toroidal core shape. Then, its magnetic properties were measured in the megahertz range. The real permeability ( $\mu '$ ) and loss tangent (tan $\delta $ ) at 10 MHz were approximately 11.19 and 0.02, respectively. The treated powder exhibited a twofold enhancement and a ten-fold reduction in the values of $\mu '$ and tan $\delta $ , respectively, in relation to the untreated Nd2Fe17N3 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.