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  • Küçük Resim
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    Electronic structure and magnetic properties of PbMO3 (M = Fe, Co, Ni) magnetic perovskites: An ab initio study
    (World Scientific Publ Co Pte Ltd, 2014) Erkisi, Aytac; Yildirim, Erdem Kamil; Gokoglu, Gokhan
    We present the electronic, magnetic and structural properties of the magnetic transition metal oxides PbMO3 (M= Fe, Co, Ni) in cubic perovskite structure. The calculations are based on the density functional theory (DFT) within plane-wave pseudopotential method and local spin density approximation (LSDA) of the exchange-correlation functional. Onsite Coulomb interaction is also included in calculations (LSDA + U). The systems are considered in ferromagnetic (FM) and G-type antiferromagnetic (G-AFM) order. FM structures are energetically more favored than G-AFM and than non-magnetic states for all the systems studied. The spin-polarized electronic band structures show that all the structures have metallic property in FM order without Hubbard-U interaction (U-eff = 0). However, the inclusion of on-site Coulomb interaction (U-eff = 7 eV) opens a semiconducting gap for majority spin channel of PbFeO3 and of PbNiO3 resulting in a half-metallic character. PbCoO3 system remains as metallic with LSDA + U scheme. Bonding features of all structures are largely determined by the hybridizations between O-p and d-states of transition metal atoms. The partial magnetic moment of Fe atom in PbFeO3 is enhanced by inclusion of Hubbard-U interaction (2.55 mu B double right arrow 3.78 mu B). Total magnetic moments of half-metallic PbFeO3 and of PbNiO3 compounds are very close to integer values.
  • Küçük Resim
    Öğe
    First-principles investigation of LaGaO3 and LaInO3 lanthanum perovskite oxides
    (Taylor & Francis Ltd, 2016) Erkisi, Aytac; Gokoglu, Gokhan; Surucu, Gokhan; Ellialtioglu, Recai; Yildirim, Erdem Kamil
    Among the class of ABO(3)-type perovskite oxides, LaMO3 (M=Ga and In) compounds are investigated in cubic (Pm-3m), tetragonal (P4mm), hexagonal (P-3m1), rhombohedral (R-3c) and orthorhombic (Pbnm) phases using generalised gradient approximation (GGA) within the density functional theory. On-site Coulomb interaction is also included in the calculations (GGA+U). After the determination of the stable phase, phase transition pressures have also been calculated. Then, their full structural, mechanical, electronic, optical and vibrational properties have been studied in stable orthorhombic (Pbnm) phase. Both compounds are non-magnetic insulators in their ground states. The energy gaps (E-g) of LaGaO3 and LaInO3 compounds have been found as 3.14 and 2.55eV, respectively. The calculated elastic constants and phonon dispersion curves confirm the stability of orthorhombic phase mechanically and dynamically.