J_(eff) = 3/2 ferromagnetic insulating state above 1000 K in a double perovskite osmate synthesized by molecular beam epitaxy

摘要

In magnetic insulating oxides, the cubic crystalsymmetry is thought to be favorable for higher Curietemperatures (TC) , since the network morphologyhosting the mechanisms of exchange interactions is subjectto the crystal symmetry. Especially for perovskites, it iswell known that the crystal symmetry dominates theexchange interactions, e.g., SrRuO_3 (pseudo-cubicperovskite, ferromagnetic metal) and CaRuO_3(orthorhombic perovskite, paramagnetic metal) . Inaddition to the symmetry, adopting 5d transition metaloxides, where spin-orbit coupling (SOC) is enhanced, is apromising way to boost the long range ferri/ferromagnetic(FM) order. For example, it was shown for a pyrochloreosmate (Cd_2Os_2O_7) that the SOC is responsible for its longrange order . Here we show that a highly B-site orderedcubic double-perovskite Sr_3OsO_6, which satisfies the abovecriteria, has the highest TC of ～1060 K among all insulatorsand oxides, and the highest magnetic ordering temperaturein any compound without 3d transition elements.