Electronic Structure And Magnetism Of Doped EuTiO₃: First-principles Studies

Based on first-principles calculations, we have studied the influence of carrier-doping on the electronic structure and magnetism of EuTiO3. We find that, when electron-doping concentration is greater than 0.1 e/f.u., EuTiO3 changes to be ferromagnetic metallic. We believe that negative spin polarizability of Ti 3d states near the Fermi level and Eu 4f exchange via O 2p orbitals are two main reasons for ferromagnetism. When hole-doping concentration is greater than 0.05 e/f.u., the system is a half-metal, owing to the large exchange splitting of the Eu 4f orbitals. Further, we have studied the A-site La and B-site Sc(Ga,Al) doped Eu TiO3. We demonstrate that Eu0.75La0.25TiO3 is a ferromagnetic metal, while EuTi0.75Sc(Ga,Al)0.25O3 exhibits ferromagnetic half-metallic. Therefore, phase diagram of carrier-doping is consistent with atom-doping results. EuTiO3 is a semiconductor with a band gap of 0.93±0.07 eV, which may be a new photovoltaic material. We have also studied the lattice, electronic and magnetic structures of the bulk EuTiO3 with GGA+U and HSE approaches. Calculated results show that the ground-state configuration of cubic EuTiO3 is a G-type antiferromagnetic insulator for Hubbard UEu=4 eV, as well as for HSE06(????????agreeing with experimental results. However, only the energy gap 0.82 e V with HSE06 approach coincides with the experimental value 0.93±0.07 eV. So HSE06?can better describe the electronic and magnetic configurations of the bulk EuTiO3.