Mn₂MnReO₆: Synthesis and Magnetic Structure Determination of a New Transition-Metal-Only Double Perovskite Canted Antiferromagnet

Transition-metal-only double perovskite oxides (A 2 BB′O 6 ) are of great interest due to their strong and unusual magnetic interactions; only one compound, Mn 2 FeReO 6, was reported in this category to date. Herein, we report the second transition-metal-only double perovskite, Mn 2 MnReO 6, prepared at high pressure and temperature. Mn 2 MnReO 6 crystallizes in a monoclinic P 2 1 / n structure, as established by synchrotron X-ray and powder neutron diffraction (PND) methods, with eight-coordinated A sites and rock-salt arrangement of the B and B′-site MnO 6 and ReO 6 . Both the structural analysis and the X-ray absorption near edge spectroscopy results indicate mixed valence states of the B/B′-site in Mn 2+ 2 Mn 2+/3+ Re 5+/6+ O 6 . The magnetic and PND studies evidence an antiferromagnetic (AFM) transition at ∼110 K and a transition from a simple AFM to canted AFM with net ferromagnetic component at ∼50 K. The observed Efros–Shklovskii variable-range-hopping semiconducting behavior is attributed to the three (A-site Mn 2+, B-site Mn 2+/3+, and B′-site Re 5+/6+ ) interpenetrating canted AFM lattices. Theoretical calculations demonstrate that the almost fully polarized Mn states in Mn 2 MnReO 6 are driven away from the Fermi level by static on-site interactions and open a small gap, which is responsible for the insulating state in such a d-electron-rich system. These results provide insight of the electronic origin of the physical properties of Mn 2 MnReO 6 with local electronic structure similar to that of Mn 2 FeReO 6 .