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

Abstract

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 BaCrO 2 H 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 BaCrO 2 H revealed an antiferromagnetic (AFM) order at T N ∼ 375 K, which is higher than ∼240 K in BaCrO 3−x F x . The relatively high T N of BaCrO 2 H 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 BaCrO 2 H in comparison with BaCrO 2 F and BaMnO 3 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.

Expanding the hydride chemistry: antiperovskites A3MO4H (A = Rb, Cs; M = Mo, W) introducing the transition oxometalate hydrides

“…[5][6][7][8] To date, oxy hydrides with isolated oxide ions represent the largest group of this materials class which includes a variety of transition metal based oxy hydrides. [9][10][11] The latter are typically synthesized by high pressure synthesis or reductive topotactic reaction which oen leads to materials with disordered anions such as AECrO 2 H (AE ¼ Sr, Ba) 10,11 or BaTiO 3Àx H x 12,13 as archetypical examples. Undoubtedly, transition metal-based oxy hydrides show fascinating characteristics on their own such as magnetic ordering at elevated temperatures 10,11,14 diffusional dynamics, 15 good electronic 13,16 or ionic 17 conductivities.…”

Isolated-Mn2+-like Luminescent Behavior in CsMnF3 Caused by Competing Magnetic Interactions at Cryogenic Temperature

“…The antiferromagnetic spin structure (Figure 4d, model 4) could be accounted for with magnetic interactions J 1 and J 2 . 54 J 1 is the interaction between corner-sharing octahedra (Mn1−Mn2), which is defined by 180°SE. Given the bridging angle (∠Mn1−F−Mn2) of 177.41°, J 1 should denote a strong antiferromagnetic interaction (J 1 < 0).…”

“…Finally, we deduced a full picture of the competitive magnetic interactions in CMF, as depicted in Figure . The antiferromagnetic spin structure (Figure d, model 4) could be accounted for with magnetic interactions J 1 and J 2 …”

“…(a) Magnetic interaction in the CsMnF: J 1 between corner-shared octahedra (Mn1–Mn2) given by 180° SE interaction and J 2 between face-shared octahedra (Mn2–Mn2) given by direct metal–metal interaction ( J 2 DE ) and 90° SE interaction ( J 2 SE ). Schematic representation of (b) direct metal–metal exchange interaction and (c) 180° type SE interaction between e g –p σ –e g (antiferromagnetic interaction, AFM), and 90°-type SE interaction (d) between e g –p σ and p π –t 2g (FM) and (e) between e g –p σx and p σy –e g (ferromagnetic interaction, FM), in d 5 configuration …”

“…Schematic representation of (b) direct metal−metal exchange interaction and (c) 180°type SE interaction between e g −p σ −e g (antiferromagnetic interaction, AFM), and 90°-type SE interaction (d) between e g −p σ and p π −t 2g (FM) and (e) between e g −p σx and p σy −e g (ferromagnetic interaction, FM), in d 5 configuration. 54 The Journal of Physical Chemistry C susceptibilities, the Mn 2+ spins in CMF are randomly oriented at room temperature. When the temperature goes down to a point that the thermal energy k B T cannot exceed J 1 , most of the spins in the neighboring corner-shared Mn 2+ octahedron block are still randomly oriented.…”