Soft magnetic properties of Co-Fe-Al-N films

This article reports on the relations between the magnetic properties and crystal structure of Co-Fe-Al-N films prepared by rf magnetron sputtering in a mixed Ar and N2 gas atmosphere. Slightly substrate-biased 4 at. % Al films showed a low coercivity of less than 80 A/m, a low magnetostriction of less than 1×10 −6, and a high saturation magnetic flux density of 1.7 T. These features were maintained after annealing at up to more than 500 °C. The low Hc was related to the crystal structure of a face-centered-cubic phase with an about 10-nm grain size. No detectable AlN was observed by an x-ray diffractometry even after annealing. However, the lattice constant after annealing was nearly equal to that of a Co-Fe alloy and the Al content increased with the increase in sputtering N2-gas content, suggesting the binding of Al and N atoms.