Induced anisotropy and permeability in amorphous Fe-B and Co-Fe-B films

Amorphous Fe-B and zero magnetostrictive Co-Fe-B films have been prepared by rf diode sputtering technique. The anisotropy of the films is reduced by annealing them at 300ÅC in a rotating field. Annealed Co-Fe-B films have small but homogeneous uniaxial anisotropy, and exhibit very low coercivity(0.015Oe) and high effective permeability (5000), whereas annealed Fe-B films have inhomogeneous anisotropy and exhibit lower permeability(1000). These permeabilities are almost constant up to 50 MHz. In Co-Fe-B films, a large anisotropy is induced by field annealing at a temperature below the pre-annealing, where the activation energy of the process is estimated to be distributed between 0.7 and 1.1 eV.