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 that is 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 (Fe
0.959
Ni
0.04
Mn
0.001
)
3
O
4
nanopowders with hydrogen gas at 1323 K. The magnetic powder cores were fabricated from Fe–X powders coated with the novel-developed phosphate insulators containing rare earth and transition metals. The insulator was more heat resistant than conventional phosphate insulators and maintained its properties even after annealing at 873 K. 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 and having a density of 7.62 Mg/m
³
, exhibited magnetic flux density at 10 kA/m of 1.66 T. Iron loss W
10/400
(B
max
= 1T, f = 400 Hz) was 38 W/kg and W
0.5/20k
(B
max
= 0.05 T, f = 20 kHz) was 43 W/kg.