Unveiling the spin polarization mechanism in half-metallic CrO2 regulated by crystal plane orientation

Abstract

The spin degree of freedom offers a foundation for reversible, energy-efficient information processing, essential for advancing spintronic and quantum information technologies. Chromium dioxide (CrO₂), with its high Curie temperature (395 K) and full spin polarization, is a promising half-metallic candidate for such applications. However, surface degradation can significantly reduce spin polarization and magnetoresistance, limiting its practical use. Improving the magnetic stability and spin polarization of CrO₂ surfaces is therefore a key challenge. Given the variation in atomic arrangement, orbital hybridization, and magnetic anisotropy across different crystallographic orientations, surface termination plays a crucial role in determining material performance. In this study, we perform first-principles calculations to investigate the (001), (110), and (100) surfaces of CrO₂, focusing on spin-resolved electronic structures, spin charge distributions, and magnetic exchange interactions. All three surfaces retain half-metallicity, with magnetism driven by Cr-3d and O-2p orbital coupling. Ferromagnetic Cr–Cr and antiferromagnetic Cr–O interactions are consistently observed. The (110) and (100) surfaces exhibit stronger spin polarization and higher magnetic moments, while the (001) surface shows greater magnetic energy stability. These results clarify the orientation-dependent mechanisms governing CrO₂'s spintronic properties and provide theoretical guidance for the design of high-performance spintronic and quantum information devices.