Soft Magnetic Properties of Microcrystalline Fe-M-C (M = V,Nb,Ta) Films with High Thermal Stability

The magnetic and structural properties of microcrystalline Fe-M-C (M = V, Nb, Ta) alloy films prepared by annealing sputter-deposited amorphous films were investigated. These new alloys are composed of α-Fe and M carbides with grain diameters of less than 10 nm. Good soft magnetic properties and high saturation flux densities of up to 1.6 T were obtained for Fe-Nb-C and Fe-Ta-C films. Suppression of the growth of α-Fe grains by fine carbide particles resulted in high thermal stability. In particular, Fe-Ta-C films exhibited a low coercive force, less than 65 A/m, even after annealing at 973 K. It was found that the magnetostriction of Fe-M-C films depends on the film composition and annealing temperature. Zero-magnetostrict ive Fe-Ta-C films with permeabilities as high as 5000 (|μ|
_1MHz
) were obtained at various annealing temperatures (823 to 923 K) by controlling the film composition.