QSGW Calculations on Electronic Structures of Co- and Mn-based Heusler Alloys

Heusler alloys show various functionalities depending on the chemical composition. Particularly, half-metallicity or spin gapless electronic structure is considered to be important for spintronics applications. So far, first-principles methods based on the density functional theory (DFT) are conveniently used for designing spintronics materials. The DFT accurately predicts ground state properties, but its reliability for the calculation of excited states is rather limited. In this study, we systematically calculate the electronic structures of Co- and Mn-based Heusler alloys by using the Quasi-particle self-consistent GW (QSGW) method, the local density approximation (LDA), and the Hybrid method (HSE06). We found that the QSGW and the LDA predict very similar electronic structure for Co₂MnSi except for a slight difference in the minority spin gap 0.77 eV (QSGW) and 0.59 eV (LDA). In addition, the QSGW predicts the Fermi level (E_F) at 0.20 eV from the VBM, but in case of the LDA the E_F is at 0.32 eV from the VBM. Such a small difference may affect magnetic excitation in this material. In contrast, the HSE06 doesn't predict half-metallic electronic structure. For typical Co- and Mn-based Heusler alloys, we discuss the difference of the calculated electronic structures around E_F.