High-Pressure Synthesis of Double Perovskite Ba2NiIrO6: In Search of a Ferromagnetic Insulator

Double perovskite oxides with d 8 -d 3 electronic configurations are expected to be ferromagnetic from the Goodenough-Kanamori rules, such as ferromagnetic La 2 NiMnO 6 . In search of new ferromagnetic insulators, double perovskite Ba 2 NiIrO 6 was successfully synthesized by high-pressure and high-temperature methods (8 GPa and 1573 K). Ba 2 NiIrO 6 crystallizes in a cubic double perovskite structure (space group: Fm 3̅ m ), with an ordered arrangement of NiO 6 and IrO 6 octahedra. X-ray absorption near-edge spectroscopy confirms the nominal Ni(II) and Ir(VI) valence states. Ba 2 NiIrO 6 displays an antiferromagnetic order at 51 K. The positive Weiss temperature, however, indicates that ferromagnetic interactions are dominant. Isothermal magnetization curves at low temperatures support a field-induced spin-flop transition.