First-principles study of electronic structure and magnetic properties of SrTi1-x M x O3 (M = Cr, Mn, Fe, Co, or Ni)

We used first-principles calculations to conduct a comparative study of the structure and the electronic and magnetic properties of SrTiO3 doped with a transition metal (TM), namely, Cr, Mn, Fe, Co, or Ni. The calculated formation energies indicate that compared with Sr, Ti can be substituted more easily by the TM ions. The band structures show that SrTi0.875Cr0.125O3 and SrTi0.875Co0.125O3 are half metals, SrTi0.875Fe0.125O3 is a metal, and SrTi0.875Mn0.125O3 is a semiconductor. The 3d TM-doped SrTiO3 exhibits various magnetic properties, ranging from ferromagnetism (Cr-, Fe-, and Co-doped SrTiO3) to antiferromagnetism (Mn-doped SrTiO3) and nonmagnetism (Ni-doped SrTiO3). The total magnetic moments are 4.0 mu B, 6.23 mu B, and 2.0 mu B for SrTi0.75Cr0.25O3, SrTi0.75Fe0.25O3, and SrTi0.75Co0.25O3, respectively. Room-temperature ferromagnetism can be expected in Cr-, Fe-, and Co-doped SrTiO3, which agrees with the experimental observations. The electronic structure calculations show that the spin polarizations of the 3d states of the TM atoms are responsible for the ferromagnetism in these compounds. The magnetism of TM-doped SrTiO3 is explained by the hybridization between the TM-3d states and the O-2p states.