Structural and electronic properties of double perovskite ruthenates; A2GdRuO6 (where A = Ba, Sr)

Abstract

We report the findings of an experimental and theoretical analysis of the structural, electronic, and vibrational characteristics of Ba 2 GdRuO 6 and Sr 2 GdRuO 6 double perovskite ruthenates. The samples of Ba 2 GdRuO 6 and Sr 2 GdRuO 6 were synthesized using solid state reaction method. The samples have been characterized by X-ray diffraction (XRD) technique where phase purity and space group information have been obtained using FullProf Rietveld refinement method. The Rietveld-fitted XRD patterns show that Ba 2 GdRuO 6 has a single-phase cubic structure with space group F m 3 ¯ m and that Sr 2 GdRuO 6 has a monoclinic structure with space group P 2 1 ∕ n . The vibrational properties were measured, via. , Raman spectroscopy performed at room temperature. The structures predicted from XRD were studied theoretical using accurate plane wave pseudo-potential method based on density functional theory (DFT) with Hubbard parameter, U (DFT+U). The Ba 2 GdRuO 6 is found to be metallic with difference in density of states for spin up and spin down electrons; whereas Sr 2 GdRuO 6 is insulating with a band gap of 4.0 eV. The vibrational analysis of pervoskites shows A 1 g , E g and 2 F 2 g , Raman active modes for Ba 2 GdRuO 6 ; while for Sr 2 GdRuO 6 the observed active modes were A g and B g , respectively . It’s worth noting that the experimentally measured values match those predicted by our DFT calculations. • An integrated experimental and theoretical approach for Ru based double perovskites has been discussed. • Future perspective to explore the role of rare-earth metal ions to further tune the electronic properties of such perovskites has been discussed. • The interesting interplay between Ru and transition metal ions can be understood as a transition from metallic for Ba 2 GdRuO 6 to insulating behavior for Sr 2 GdRuO 6 .