Half-metallicity in CrAl-terminated Co₂CrAl thin film

Half-metals with high Curie temperature are ideal candidates for applications in spintronics. Many half-metallic materials have been predicted theoretically, and some have been confirmed experimentally. At the same time, in thin-film geometry the electronic structure of these materials may change due to the potential presence of surface/interface states, which could limit practical applications of these materials in nano-size devices. Here, from first principles we study a full Heusler compound, Co₂CrAl in thin film geometry. This material has been studied extensively, and it has been reported that it exhibits half-metallic properties in the bulk. We show that this material retains 100% spin polarization in CrAl-terminated thin film geometry (Co-termination results in destroyed half-metallicity) as well. Moreover, we confirm that under biaxial strain Co₂CrAl retains half-metallicity for a practically feasible range of considered pressure. The magnetic alignment of Co₂CrAl is confirmed to be ferromagnetic, with the non-integer total magnetic moment of Co-terminated cell, and the integer total magnetic moment of CrAl-terminated cell. If confirmed experimentally, these results may have an important impact in spin-based electronics.