High-Frequency Magnetic Properties of Novel Sm-Mo-Fe Phosphate-Coated Fe-X (X = Ni and Mn) Magnetic Powder Cores

In this study, we developed a new magnetic powder core using Fe- X powders, which has a coercivity of less than 80 A/m and a saturation magnetization comparable to that of pure iron powders. Fe- X powders doped with 4 at% nickel and 0.1 at% manganese were fabricated by the reduction of Ni-Mn doped ferrite (Fe0.959Ni0.04Mn0.001)(3)O-4 nanopowders with hydrogen gas at 1323 K. The magnetic powder cores were prepared from Fe- X powders coated with the novel phosphate insulators developed using rare earth and transition metals. The as-produced insulator was more thermally stable than conventional phosphate insulators and maintained its properties even after annealing at 873 K. After annealing, the Sm-Mo-Fe phosphate insulating layer separated into a samarium-rich and transition-metal-rich layer. The magnetic powder core of Fe-X(X = Ni and Mn) powders coated with the Sm-Mo-Fe phosphate insulator, compacted at 1.47 GPa with heat treatment at 793 K, having a density of 7.62 Mg/m(3), and exhibited magnetic flux density at 10 kA/m of 1.66 T. Iron loss W-10/400 (B-max = 1 T, f = 400 Hz) was 38 W/kg and W-0.5/20 k (B-max = 0.05 T, f = 20 kHz) was 43 W/kg.