Half-metallic ferromagnetism and metal-insulator transition in Sn-doped SrRuO3 perovskite oxides

We investigate the electronic and magnetic properties of SrRu1-xSnxO3 by carrying out density-functional-theory calculations to show that a half-metallic ferromagnetic ground state emerges for the Sn doping of x greater than or similar to 0.5. To examine the effect of on-site Coulomb interactions for the Ru d orbitals, which was suggested to enhance the half-metallicity in SrRuO3, we employed both the local spin-density approximation (LSDA) as well as the LSDA + U method. For all the possible configurations of Sn doping for x = 1/8; 1/4; 1.2; 5/8; 3/4, and 7/8 within the 2 x 2 x 2 unit cell, we monitor the Ru t(2g) bandwidth as well as the valence band maximum in the majority-spin channel and demonstrate that the Ru d electron hopping is blocked by the Sn-substituted sites so that the Ru t(2g) bandwidth becomes reduced as the doping x increases. For x < 0.5, the valence band maximum still touches the Fermi level so that SrRu1-xSnxO3 remains as a usual ferromagnetic metal. A further reduction of the Ru t(2g) bandwidth for the range of 0.5 less than or similar to x less than or similar to 0.7 turns it into a half-metallic ferromagnet. As for x > 0: 7, the Ru t(2g) bandwidth gets so narrow that even a small on-site Coulomb interaction, e.g., U-eff = 1: 0 eV induces a band-gap, which indeed corresponds to a gap of the Ru impurity bands in the SrSnO3 oxide semiconductor. (C) 2018 Elsevier B.V. All rights reserved.