Magnetic properties of multilayered Fe-C film formed by dual ion beam sputtering

The magnetic properties of both single-layered and multilayered Fe-C films formed by dual ion beam sputtering are studied. When the C concentration in Fe-C films increases, the relative permeability of the film increases and the coercivity decreases. The relative permeability of single-layered Fe-9at%C film with a magnetostriction constant nearly zero, is 550 at 5 MHz, even though that of pure Fe is only 150. When a multilayered film is made by alternating 5nm thick permalloy intermediate layers with 95nm thick Fe-C films, the soft magnetic properties of the resulting film show tremendous improvement. Multilayered Fe-9at%C film shows a relative permeability of 1400 and a coercivity of 200A/m. Compressive stress up to -2 × 10⁹N/m²exists in this film. This stress can be relieved by heat treating the film in Ar, which improves the soft magnetic properties. The Fe-9at%C/permalloy multi-layered film annealed for 1 hour at 400°C shows a saturation magnetic flux density of 2.1T, a relative permeability of 3000 and a coercivity of 80 A/m.