Soft magnetic properties for Fe-Al-Nb-N-O films

Magnetic and other properties of fine-crystal Fe-N films with additional Al, Nb, and O were investigated. Films were prepared by RF planar magnetron sputtering. The grain size and the lattice spacing were changed by the addition of Al and Nb, and the coaddition of Al and Nb was found to be effective in improving the soft magnetic properties of the films after annealing at 550°C. Introducing oxygen into the sputtering gas of argon and nitrogen increased the nitrogen concentration in the films and was effective in reducing the coercivity of the films. The magnetostriction of the films changed from negative toward positive with increasing nitrogen concentration and crossed zero at the nitrogen concentration where the coercivity had a minimum value. Hardness measurement of the films revealed that the addition of Al and Nb prevents recrystallization in Fe films as well as in Fe-N-O films. The (Fe_97.5Al_1.1Nb_1.4)₉₂N ₆O₂ films exhibited a saturation magnetic flux density of 20 kG, a coercivity of 0.3-0.5 Oe, and a hardness above 1000 even after annealing at 550°C without magnetic field application