First principle research of possible HM-AFM in double perovskites A ₂MoOsO₆ and A₂TcReO₆ (A = Si, Ge, Sn, and Pb) with group IVA elements set on the A-site position

We calculated electronic structures of double perovskite structures of A₂MoOsO₆ and A₂TcReO₆ (A = Si, Ge, Sn, and Pb) based on the density functional theory which was carried out with a full structural optimization using generalized gradient approximation and taking into account the correlation effect (GGA + U). In GGA calculation, Pb ₂TcReO₆ shows a half-metallic antiferromagnet (HM-AFM) characteristic, whereas Sn₂MoOsO₆, Pb ₂MoOsO₆, and Sn₂TcReO₆ are nearly HM-AFMs. With GGA + U calculation, Sn₂MoOsO₆ and Pb ₂MoOsO₆ become stable HM-AFM, but Sn₂TcReO ₆ and Pb₂TcReO₆ changes HM-AFM into an antiferromagnetic insulator. The p-d hybridization between B(B′) _d-O_p and double exchange interaction is the mean reason to result in the half-metallic and compensated ferrimagnetic phase.