Magnetic Properties of Fe-Co-Nb Thin Films

The dependence of the soft magnetic properties of sputtered (Fe
_1-x
Co
_x
)
_1-y
films (0≤X≤1.0, 0≤Y≤0.2 in weight fractions) on the composition and annealing temperature was studied. Films with Y≤0.16 were amorphous, while films with Y≤0.16 have bec structure for 0≤X≤0.8 and fcc structure for 0.8≤X≤1.0. The lattice constant of the bec films increases with Nb content. The coercivity of films annealed at 773K for 3600 s exhibits a minimum of 400 A/m around Y= 0.05 and X= 0.3 to 0.8. The corresponding permeability and saturation magnetic flux density are 800 and 2 T respectively. The coercivity strongly depends on the expansion of the lattice constant the addition of Nb, and takes on a minimum when the lattice constant of Fe-Co film is expanded by 0.2%.