Large magnetocrystalline anisotropy in bilayer transition metal phases from first-principles full-potential calculations - art. no. 144409

The computational framework of this study is based on the local-spin-densit y approximation with first-principles full-potential linear muffin-tin orbi tal calculations including orbital polarization (OP) correction. We have st udied the magnetic anisotropy for a series of bilayer CuAu(I)-type material s such as FeX, MnX (X = Ni,Pd,Pt), CoPt, NiPt, MnHg, and MnRh in a ferromag netic state using experimental structural parameters to understand the micr oscopic origin of magnetic-anisotropy energy (MAE) in magnetic multilayers. Except for MnRh and MnHg, all these phases show perpendicular magnetizatio n. We have analyzed our results in terms of angular momentum-, spin- and si te-projected density of states, magnetic-angular-momentum-projected density of states, orbital-moment density of states, and total density of states. The orbital-moment number of states and the orbital-moment anisotropy for F eX (X = Ni,Pd,Pt) are calculated as a function of band filling to study its effect on MAE. The total and site-projected spin and orbital moments for a ll these systems are calculated with and without OP when the magnetization is along or perpendicular to the plane. The results are compared with avail able experimental as well as theoretical results. Our calculations show tha t OP always enhances the orbital moment in these phases and brings them clo ser to experimental values. The changes in MAE are analyzed in terms of exc hange splitting, spin-orbit splitting, and tetragonal distortion/crystal-fi eld splitting. The calculated MAE is found to be in good agreement with exp erimental values when the OP correction is included. Some of the materials considered here show large magnetic anisotropy of the order of meV. In part icular we found that MnPt will have a very large MAE if it could be stabili zed in a ferromagnetic configuration. Our analysis indicates that apart fro m large spin-orbit interaction and exchange interaction from at least one o f the constituents, a large crystal-field splitting originating from the te tragonal distortion is also a necessary condition for having large magnetic anisotropy in these materials. Our calculation predicts large orbital mome nt in the hard axis in the case of FePt, MnRh, and MnHg against expectation .