Comparative study of tight-binding and ab initio electronic structure calculations focused on magnetic anisotropy in ordered CoPt alloy

• Calculations of electronic structure properties of bulk ordered CoPt alloy using tight-binding (TB) and density functional theory (DFT) approach.
• Refinement of existing single-element TB parameters for a binary alloy based on a comparison of band structure and spin magnetic moment per atom to DFT results.
• Quantitative agreement of magnetic anisotropy energy (MAE) obtained by TB and DFT on a range of band fillings.
• Successful description of ground state spin–orbit coupling phenomena using an extended TB model suitable for subsequent magnetotransport simulations.

An empirical multiorbital (spd) tight binding (TB) model including magnetism and spin–orbit coupling is applied to calculations of magnetic anisotropy energy (MAE) in CoPt L10 structure. A realistic Slater–Koster parametrisation for single-element transition metals is adapted for the ordered binary alloy. Spin magnetic moment and density of states are calculated using a full-potential linearised augmented plane-wave (LAPW) ab initio method and our TB code with different variants of the interatomic parameters. Detailed mutual comparison of this data allows for determination of a subset of the compound TB parameters tuning of which improves the agreement of the TB and LAPW results. MAE calculated as a function of band filling using the refined parameters is in broad agreement with ab initio data for all valence states and in quantitative agreement with ab initio and experimental data for the natural band filling. Our work provides a practical basis for further studies of relativistic magnetotransport anisotropies by means of local Green's function formalism which is directly compatible with our TB approach.