First-principles study of half-metallic materials in double-perovskite A ₂FeMO ₆ (M = Mo, Re, and W) with IVA group elements set on the A-site position

In this work, calculations based on density functional theory were carried out with full structural optimization and using the generalized gradient approximation (GGA). In addition, the correlation effect (GGA+U) in the double-perovskite structure A ₂BB′O ₆ (A = Si, Ge, Sn, and Pb) is considered. As the valence electrons between IIA (s ²) and IVA (p ²) are similar, the IVA group of elements is settled on the A-site ion position with fixed BB′ combinations as FeM (M = Mo, Re, and W). The p-d hybridization with double exchange is the main course of the ferrimagnetic half-metallic properties. For M = Mo and Re, all compounds can be half-metallic (HM) materials, with Si ₂FeReO ₆ and Ge ₂FeReO ₆ recommended for the GGA+U process. For M = W, only A = Sn and Pb are suitable options for HM materials. However, considering that Si, Ge, Sn, and Pb are quite different from Sr, an examination of structural stability is needed. All compounds are found to be stable, except for the Si-based double-perovskite structure.