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 TN ∼ 375 K, which is higher than ∼240 K in BaCrO3-xFx. The relatively high TN 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.