ANOMALOUS PERPENDICULAR MAGNETOANISOTROPY IN MN4N FILMS ON SI(100)

Ferrimagnetic Mn4N films were deposited on Si (100) substrate by dc reactive magnetron sputtering from sintered Mn target. Highly (002) textured Mn4N ordered phase is formed in situ at studied substrate temperatures of 150-250°C without further annealing. Anomalous perpendicular magnetoanisotropy exists in these face-centered cubic films with larger coercivity measured perpendicular to the film (2000-3000 Oe) than that parallel (1100-1300 Oe), as is the remanence. Coercivity in either direction decreases, while the saturation flux density (from 240 to 610 G) increases with increasing substrate temperature. The anomalous perpendicular magnetoanisotropy is attributed to (1) the stress-induced anisotropy due to in-plane tensile stress coupled with a reverse magnetostriction, and (2) the shape anisotropy due to columnar grain structure.