Magnetic anisotropy of L1[formula omitted] FeNi (001), (010), and (111) ultrathin films: A first-principles study.

In previous experiments, L1 0 FeNi thin films with different surfaces, including (001), (110), and (111), were produced and studied. Each surface defines a different alignment of the crystallographic tetragonal axis with respect to the film's plane, resulting in different magnetic anisotropies. In this study, we use density functional theory calculations to examine three series of L1 0 FeNi films with surfaces (001), (010), and (111), and with thicknesses ranging from 0.5 to 3 nm (from 4 to 16 atomic monolayers). Our results show that films (001) have perpendicular magnetic anisotropy, while (010) favor in-plane magnetization, with a clear preference for the tetragonal axis [001]. We proposed calling this type of in-plane anisotropy fixed in-plane. A film with a surface (111) and a thickness of four atomic monolayers has a magnetization easy axis almost perpendicular to the plane of the film. As the thickness of the (111) film increases, the direction of magnetization rotates towards a tetragonal axis [001], positioned at an angle of about 45° to the plane of the film. Furthermore, the most significant changes in spin and orbital magnetic moments occur at a depth of about three near-surface atomic monolayers. Ultrathin L1 0 FeNi films with varying magnetic anisotropies may find applications in spintronic devices. • The (111) surfaces of L10 FeNi film is more stable than (001) and (010) surfaces. • In films (001) and (010), easy magnetization direction is the tetragonal axis [001]. • For thicker (111) films, easy magnetization direction is [001] (45 deg to the plane). • For ultrathin (111) films it deviates from [001] towards [111] (normal to the plane). • Magnetic anisotropy of thinnest (111) films resembles perpendicular anisotropy. [ABSTRACT FROM AUTHOR]