First-Principle Calculations of Magnetic Properties of Hexagonal BaTi0.95TM0.05O3−δ ; TM = [Fe, Cr, Co

Abstract

We have studied the magnetism in the hexagonal polymorph of BaTiO3 doped with one of the transition metals (TM = Co, Fe, Cr) and in the presence of oxygen vacancies. The formation energies for BaTi0.95TM0.05O3−δ; (TM = Co, Fe, Cr) are 8.10, 8.80, and 12.36 eV, respectively. The antiferromagnetic (AFM) phase of BaTiO3 has changed to a ferromagnetic phase because of doping. For each case of doping, the transition metal induced a non-negligible magnetic moment in the structure BaTi0.95TM0.05O3. Furthermore, the amount of oxygen defects influences directly the total magnetic moment and also the electronic conduction properties. For BaTi0.95Co0.05O2.95, we have found that the system is half metallic ferromagnet and the magnetic moment is reversed with respect to oxygen vacancy free system. The half metallic character is also present in BaTi0.95Cr0.05O2.95 but with no flipping of the total magnetic moment. For BaTi0.95TM0.05O2.5 systems, the magnetic structure is ferromagnetic and the influence of oxygen vacancy concentration is shown in the enhancement of the ferromagnetic state.