Enhanced Magnetic Interaction by Face-Shared Hydride Anions in 6H-BaCrO2H

Studies on magnetic oxyhydrides have been almost limited to perovskite-based lattices with corner-sharing octahedra with a M–H–M (M: transition metal) angle of θ ∼ 180°. Using a high-pressure method, we prepared BaCrO2H with a 6H-type hexagonal perovskite structure with corner- and face-sharing octahedra, offering a unique opportunity to investigate magnetic interactions based on a θ ∼ 90° case. Neutron diffraction for BaCrO2H revealed an antiferromagnetic (AFM) order at T N ∼ 375 K, which is higher than ∼240 K in BaCrO3–x F x . The relatively high T N of BaCrO2H can be explained by the preferred occupancy of H– at the face-sharing site that provides AFM superexchange in addition to AFM direct exchange interactions. First-principles calculations on BaCrO2H in comparison with BaCrO2F and BaMnO3 further reveal that the direct Cr–Cr interaction is significantly enhanced by shortening the Cr–Cr distance due to the covalent nature of H–. This study provides a useful strategy for the extensive control of magnetic interactions by exploiting the difference in the covalency of multiple anions.