Room Temperature Ferromagnetic Spin Ordering in Multiferroic Double Perovskite Oxides

Room temperature ferromagnetic (neither ferrimagnetic nor canted antiferromagnetic) spin ordering is here designed in a predictive way and demonstrated experimentally for the first time with Curie temperature TC(FM) > 450K within synthesizable d
⁵
-d
³
/d
⁰
solid solution double-perovskite oxides. Meanwhile, a Volcano-shaped trend between Weiss temperature Θ and μ × rA/rB ensemble descriptor (μ, rA and rB are reduced mass of primitive cell, A-site cation radius and B-site cation radius, respectively) was observed and able to quantitatively predict chemical composition of double-perovskite oxide for various spin ordering including ferromagnetism, spin frustration and ferrimagnetism. Lattice symmetry, optical bandgap and insulating properties were also characterized experimentally and prospect for room temperature ferromagnetic semiconductor discussed.