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

摘要

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 (LSDAU) 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 (Δm) 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 Δm 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~2oe_g~0 of GoodenoughKanamoriAnderson (GKA).