MnFe0.5Ru0.5O3: an above-room-temperature antiferromagnetic semiconductor

Abstract

A transition-metal-only MnFe_0.5Ru_0.5O₃ polycrystalline oxide was prepared by a reaction of starting materials MnO, MnO₂, Fe₂O₃, RuO₂ at 6 GPa and 1873 K for 30 minutes. A combination of X-ray and neutron powder diffraction refinements indicated that MnFe_0.5Ru_0.5O₃ adopts the corundum (α-Fe₂O₃) structure type with space group Rc, in which all metal ions are disordered. The centrosymmetric nature of the MnFe_0.5Ru_0.5O₃ structure is corroborated by transmission electron microscopy, lack of optical second harmonic generation, X-ray absorption near edge spectroscopy, and Mössbauer spectroscopy. X-ray absorption near edge spectroscopy of MnFe_0.5Ru_0.5O₃ showed the oxidation states of Mn, Fe, and Ru to be 2+/3+, 3+, and ∼4+, respectively. Resistivity measurements revealed that MnFe_0.5Ru_0.5O₃ is a semiconductor. Magnetic measurements and magnetic structure refinements indicated that MnFe_0.5Ru_0.5O₃ orders antiferromagnetically around 400 K, with magnetic moments slightly canted away from the c axis. ⁵⁷Fe Mössbauer confirmed the magnetic ordering and Fe³⁺ (S = 5/2) magnetic hyperfine splitting. First principles calculations are provided to understand the electronic structure more thoroughly. A comparison of synthesis and properties of MnFe_0.5Ru_0.5O₃ and related corundum Mn₂BB′O₆ derivatives is discussed.