A DFT study on the austenitic Ni2MnGa (001) surfaces

Through the use of spin-polarized density functional theory calculations we have studied the different (001) surface terminations of austenitic Ni2MnGa. The stability analysis revealed a preference to form MnGa terminated surfaces in a large range of growth conditions, Ni-terminated surfaces are stable as well. The dominant structure, is the one engineered to be Ga-terminated, but that appears under Ga-rich conditions. STM images were simulated for all surface terminations and compared with the images obtained experimentally by Leicht et al. New J. Phys. 13 (2011) 033021. We found a perfect match between theory and experiment for MnGa and Ni terminations. From the STM images of the MnGa termination, the Mn atoms are strongly imaged, while the Ga atoms are weak. Whereas for the Ni terminated surface, there is a large local density of states due to the Ni atoms with an appreciably contribution due to the second monolayer Mn atoms. Magnetic characterization revealed surface effects on the MnGa and Ni terminated surfaces, whereas the Ga terminated experienced no change. Our results give insight about what is observed in the experimental STM images. (C) 2020 Elsevier B.V. All rights reserved.