Magnetic Properties of Fe-Co-Nb Thin Films

The dependence of the soft magnetic properties of sputtered (Fe1-xCox)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%.