Magnetic properties of Fe-Zr-N soft magnetic thin films

Thin films of Fe-Zr-N were fabricated by r.f.-sputtering method. Their saturation magnetization and coercivity were studied as a function of annealing temperature and partial pressure of nitrogen gas. Also the effective permeability at high frequences and thermal stability were investigated fora series of samples. The films exhibit good magnetic softness in the range of composition Fe₇₂÷₇₈Zr₇₁÷₁₀N₁₅÷₁₈ which defines the limit between polycrystalline and amorphous structures. The films showing the best softness exhibit the saturation flux density 1.55 T and the effective permeability around 3000 at 1 MHz. These films show also good thermal stability (their permeability drops to 2500 when the sample is heated up as high as to 550°C). It seems that good magnetic softness of the films is due to the precitipations of Zr-N nanocrystals (their size 1÷1.5 nm) which restrain the growth of a-Fe grains (4÷5 nm).