Strain and Stress in Magnetoelastic Co–Pt Multilayers

The influence of substrate strain on the magnetic properties of Co-Pt multilayers is investigated by density functional theory (DFT) and model calculations. The lattice parameters for strained Co-Pt multilayers, which are needed as an input for first-principle calculations, are determined by a hybrid approach where DFT is used to determine the lattice constants and atomic positions of the free multilayer, and the effect of the strained substrate is treated continuum mechanically. The lowest order anisotropy constants have been calculated for unstrained and strained hcp Co₂Pt₄(111) and fcc Co₁Pt₅(111) multilayers on LiNbO₃, and in the strained case, the anisotropy is nonunixial with nonzero anisotropy constant K₁ and K₁´. By involving both multilayer and substrate mechanical properties, our calculations go beyond the usually considered magnetoelastic anisotropy mechanisms.