The iron nitride(Fe-N) thin films were deposited using a DC magnetron sputtering system. The dependence of the crystallographic characteristics and magnetic properties (Ms, Hc) on the deposition power and nitrogen input ratio $F_{N_2}/F_{total}$ was investigated. The effects of lattice distortion on the microstructure and the coercivity were discussed. The film deposited at low nitrogen input ratios had a distorted α-Fe structure and as nitrogen input ratio increased, hcp $Fe_{2-3}N$ and orth $Fe_2N$ phases were formed. At low nitrogen inlput ratios the films showed a saturation magnetization, 4πMs, of about 20kG which is close to that of pure bulk iron. The saturation magnetization was markedly decreased with formations of $Fe_{2-3}N$ and $Fe_2N$ phases. The coercivity was also strongly dependent on nitrogen input ratio. These results were consistent throughout all deposition power conditions. The dependence of coercivity on nitrogen gas input ratio was closely related with the lattice distortion which results from nitrogen solid solution effects. The film which has low coercivity had a fine grained structure with a smooth surface. The decrease of coercivity could be attributed to disordered columnar growth which is caused by lattice distortion. A small coercivity of 0.94Oe was obtained from the films deposited at 30W, $F_{N_2}/F_{total}$=6%.
