Improvement of soft magnetic properties of FeCo core alloy by vacuum and field annealing

Microstructures and soft magnetic properties of FeCo alloy were investigated in an attempt to improve its soft magnetic properties. Microstructural dependence of the magnetic properties was studied by vacuum annealing at various temperatures. Magnetic field annealing was performed to study the dependence of the coercivity on the magnetic filed applied during annealing. The field annealing effect was observed only for the alloys after recrystallization, and was increased with the increase of the applied field within the range of 2.0×10⁴ A/m (250 Oe). Coercivity of the FeCo alloys was decreased to 72 A/m (0.9 Oe) after annealing with a magnetic field of 1.76×10⁴ A/m (220 Oe) at 850°C. The microscopic mechanism of the field annealing effect was also discussed in terms of magnetostrictive characterization.