High-temperature AC magnetic properties of FeCo-based soft magnets

The temperature dependence of AC magnetic properties of soft magnetic Co₂₇Cr_0.6Ni_0.6Fe_bal alloys has been studied. Microstructural characterization indicates that the alloy has a disordered BCC structure which is insensitive to heat-treatment. At low frequencies, the alloy shows a low coercivity H_c, high saturation magnetization M_s, and high magnetic permeability μ_m. As the frequency increases, all those properties deteriorate due to the damping of magnetic domain walls. On the other hand, H_c and M_s, decrease, and μ_m increases with increasing temperature in the range of 20-600°C. The change of H_c and μ_m with temperature is attributed to the variation of magnetocrystalline anisotropy K₁, which also improves the core loss at high temperature.