High-Pressure Synthesis and Ferrimagnetic Ordering of the B-Site-Ordered Cubic Perovskite Pb 2 FeOsO 6 .

Pb2 FeOsO6 was prepared for the first time by using high-pressure and high-temperature synthesis techniques. This compound crystallizes into a B-site-ordered double-perovskite structure with cubic symmetry Fm3̅m, where the Fe and Os atoms are orderly distributed with a rock-salt-type manner. Structure refinement shows an Fe-Os antisite occupancy of about 16.6%. Structural analysis and X-ray absorption spectroscopy both demonstrate the charge combination to be Pb2 Fe3+ Os5+ O6 . A long-range ferrimagnetic transition is found to occur at about 280 K due to antiferromagnetic interactions between the adjacent Fe3+ and Os5+ spins with a straight (180°) Fe-O-Os bond angle, as confirmed by X-ray magnetic circular-dichroism measurements. First-principles theoretical calculations reveal the semiconducting behavior as well as the Fe3+ (↑)Os5+ (↓) antiferromagnetic coupling originating from the superexchange interactions between the half-filled 3d orbitals of Fe and t2g orbitals of Os.