Roles of the band filling and the d orbitals hybridization on the conduction and magnetism of some Sr-based double perovskites: An LSDA+U study

We have systematically investigated the electronic structure and magnetic properties of the double perovskite oxides Sr2CrZrO6, Sr2MnNbO6, Sr2FeMoO6 and Sr2NiRuO6 in terms of band filling of different t2g and eg orbitals. Calculations of density of the states (DOS) were performed within the frame of the local spin density approximation and Hubbard potential (LSDA+U) employed in the Linear Muffin Tin Orbitals with Atomic Sphere Approximation (LMTO-ASA) method. The DOS of Sr2FeMoO6 was obtained and found to agree very well with published reports. Half-metallic character through the spin-down channel and the ferrimagnetic ordering was observed with notable hybridization among the 3d, p and 4d orbitals within Fermi level. A difference between the theoretically expected values and the calculated ones for the magnetic moment (Δm) of the 3d orbitals is determined and had been found to increase on going from Sr2CrZrO6 to Sr2NiRuO6. This increment in Δm indicates increment in the hybridization strength, which leads to long range ordering in Sr2FeMoO6 and Sr2NiRuO6 compounds. In comparison with reported experiments, the frustrated magnetism and weak ferrimagnetism states are the most possible ones in Sr2CrZrO6 in Sr2MnNbO6, respectively. The half-metallic character was also seen in Sr2MnNbO6 and Sr2CrZrO6 compounds while Sr2NiRuO6 shows normal metallic conduction and ferromagnetism in accordance with the superexchange interaction eg2–o–eg0 of Goodenough–Kanamori–Anderson (GKA).