Significant improvement of soft magnetic properties for FeCoSiBC amorphous alloy cores by magnetic field annealing

The static and dynamic soft magnetic properties as well as the magnetic domain structure for Fe_82-xCo_xSi₄B₁₃C₁ (x = 0 ~ 30) alloy cores after normal annealing (denoted as “NA”) and longitudinal/transverse magnetic field annealing (denoted as “LA” and “TA”) were investigated. It shows that both LA and TA has little effect on the saturation magnetization (B_s), but they significantly reduce the coercivity (H_c) and core losses (P_cm) compared to NA. After TA, the 15 at% Co samples are more likely to achieve constant permeability properties in comparison to samples without Co addition. After LA, the sample with 15 at% Co addition reaches a minimum H_c of 8.3 A/m, while after TA, the P_1.5/50 reaches a minimum of 0.58 W/kg. The samples with 15 at% Co have a higher operating point, especially at 1.6 T, exhibiting lower P_cm than the samples without Co after TA. The excellent soft magnetic properties of LA and TA samples are attributed to the induced anisotropy resulting in wide striated domains separated by straight and smooth walls. The amorphous alloy seems to be an alternative material for applications in the field of electric motors.