Effect of substrate-film interface on magnetic properties of Mn4N films

Ferrimagnetic Mn4N thin films were deposited on blank Si(100), SiNx-coated Si(100) and polyimide-coated Si(100) substrates by dc reactive magnetron sputtering. Ordered Mn4N structure with (002) texture was identified in these films at substrate temperatures from 150 to 250 degrees C without further annealing. The films on blank Si(100) and SiNx-coated Si(100) exhibit much higher coercivity than those on polyimide-coated Si(100). However all films show a perpendicular coercivity of around two times higher than parallel coercivity. The saturation flux density is 240 to 610 G, increasing with elevated substrate temperature. The interface between substrate and film is found to dominate residual stress in films and to affect the absolute value of coercivity. The abnormal perpendicular magneto-anisotropy of these films is attributed to the columnar grains with ordered (002) structure and stress effect.