Nano-materials design for High-T _C ferromagnets of Ti _1-xCoxO ₂ nanosheets

We present materials design of high-T _C ferromagnetic nanomaterials based on first-principles calculations. Two-dimensional (2D) titania nanosheet, a recently discovered room-temperature (RT) ferromagnetic nanomaterial, is an important target for 2D ferromagnets. In Ti _1-xCo _xO ₂ nanosheets with Co ²⁺ oxidation state, the ferromagnetic states are highly stabilized up to x = 0.5 with a modest doping dependence of magnetic moment (~1 μ _B/Co). Moreover, we find that tailoring properties could be achieved by tuning Co oxidation states, and the optimally doped Ti _1-xCo _xO ₂ nanosheets (Co ³⁺; x = 0.125, 0.25) are found to be an excellent RT half-metallic ferromagnet with a large magnetic moment (~4 μ _B/Co). 2D nanosheet is therefore expected to provide a very useful platform for nanoscale spinelectronics devices.