High anisotropic magnetoresistance, perfect spin-filtering effect, and negative differential resistance effect of Cr-doped anatase phase TiO2

Abstract

Anisotropy-based half-metallic materials are highly efficient in spintronic devices and have important applications in spintronics. Anatase phase TiO2 has attracted much attention because of its anisotropy, but its non-magnetism limits its applications in spintronics. We investigate the electronic structure of 3d transition metal-doped anatase phase TiO2 by first principles method to achieve spin injection of anatase. The calculation results exhibit that the Sc, Cr, Mn, Fe, and Ni-doped systems are half-metallic ferromagnets while other doped systems behave as magnetic metals except the V-doped system is a magnetic semiconductor. The calculated formation energy under O-rich condition are negative shows that all half-metals are thermodynamically stable, and we construct devices along the y-direction of the half-metal and find that the device based on the Cr-doped system has the best electronic transfer capacity under zero bias. Then we use the Cr-doped system as the electrode and the pure anatase unit cell as the central scattering region to construct devices in different directions. We find that the magnitude of the current along different transport directions varied greatly, and the calculated anisotropic magnetoresistance was as high as 300%. Furthermore, whether spin configurations (PC) or antiparallel configurations (APC), there is a 100% spin-filtering efficiency of the device, and we find a significant negative differential resistance effect of the device in PC. These results suggest that Cr-doped anatase phase TiO2 can be used in spintronics.