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.

High saturation magnetic flux density Co-Fe-AI-N films were prepared by rf sputtering in a mixed Ar and N2 gas atmosphere with the Al content as a parameter. 1 at. % Al films showed a high coercive force (Hc) of more than 2000 AIm, a grain size of about 30 nm and an fcc (lOO) preferred orientation. 3-5 at.% Al films showed good softness with an Hc of less than 80 A/m. a fine grain size of about 10 nm and the disappearance of the fcc (lOO) preferred orientation. 8 at.% Al films showed slightly higher Hc than that of 3-5 at. % Al films in spite of the same fine grain size as or less than that of 3-5 at. % AI films. The lattice constant did not change by increasing the Al content to 8 at. %. No AIN was detected by XPS and diffraction patterns for 4 at. % Al films. though it was detected for 8 at. % Al films.

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