Theoretical estimation of surface magnetic anisotropy on L10-FePt thin films: Case of perfect and defect Surfaces

•Estimation of value and direction of L10−FePt surface anisotropies using a phenomenological model.•Relationship between structural magnetic and electronic properties and surface anisotropy.•Dependence of the surface anisotropy on the film thickness,and the atomic environment of the surface layer.•Impact of surface atomic concentration to the value and the direction of surface anisotropies. [Display omitted] We carried out first-principle calculations of magnetocrystalline anisotropy of L10-FePt thin films terminated by either perfect Fe (Pt) layers or defect surfaces, including vacancies or substituted surface atoms. Inspired by the experimental strategy for determining magnetic anisotropy, we present here a theoretical model for analyzing volume and surface magnetic anisotropies for L10-FePt thin films with different surface terminations. We demonstrate that surface anisotropy does not depend solely on the film thickness, but also on the atomic environment of the surface layer. Perpendicular surface anisotropy of L10-FePt thin films reaches its maximum with full Pt termination, which decreases with increasing Pt vacancies and becomes parallel to the surface for a full Fe surface. In the case of mixed surfaces, surface anisotropy of (3Pt,1Fe) is enhanced compared to platinum-rich surface with one vacancy, and tends to be more in-plane for an iron-rich surface (3Fe,1Pt). Our results could be used to study surface anisotropy effects on L10-FePt surfaces by mean of classical magnetic models, and they are very promising for the development of high density magnetic data storage such as magnetic memory.