Tuning the ferromagnetism of a single layered titanium dioxide nanosheet with hole doping and uniaxial strain.

The effects of hole doping and strain on the electronic and magnetic properties of a single layered TiO2 nanosheet were investigated here. It is found that the spontaneous magnetism can be introduced in all systems doped with low valence metal, indicating holes are the key fact to trigger local magnetic moments. Especially, a half-metal magnetism takes place when Li substitutes a Ti atom. As for the stability of dopants, the Al doping case shows lower formation energy than those of Li and Mg doping under O-rich conditions. Tuning the hole concentration, a phase transition from nonmagnetic to half-metal ferromagnetic ground state can emerge after the average spin magnetic moment reaches 1.0 µ B /hole. Furthermore, the uniaxial strain effectively adjusts the magnetism by shifting the main peak of density of states near the fermi level. The anisotropic transition of magnetic state under uniaxial tensile strain was observed due to the competition of orbital hybridization between Ti and O atoms along different crystal directions.