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

Abstract

We have systematically investigated the electronic structure and magnetic properties of the double perovskite oxides Sr 2CrZrO 6, Sr 2MnNbO 6, Sr 2FeMoO 6 and Sr 2NiRuO 6 in terms of band filling of different t 2g and e g 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 Sr 2FeMoO 6 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 (Δ m) of the 3d orbitals is determined and had been found to increase on going from Sr 2CrZrO 6 to Sr 2NiRuO 6. This increment in Δ m indicates increment in the hybridization strength, which leads to long range ordering in Sr 2FeMoO 6 and Sr 2NiRuO 6 compounds. In comparison with reported experiments, the frustrated magnetism and weak ferrimagnetism states are the most possible ones in Sr 2CrZrO 6 in Sr 2MnNbO 6, respectively. The half-metallic character was also seen in Sr 2MnNbO 6 and Sr 2CrZrO 6 compounds while Sr 2NiRuO 6 shows normal metallic conduction and ferromagnetism in accordance with the superexchange interaction e g 2–o–e g 0 of Goodenough–Kanamori–Anderson (GKA).