Correlated proton disorder in the crystal structure of the double hydroxide perovskite CuSn ( OH ) 6

作者：Anton A. Kulbakov, Ellen Häußler, Kaushick K. Parui, Aswathi Mannathanath Chakkingal, Nikolai S. Pavlovskii, Vladimir Pomjakushin, Laura Cañadillas‐Delgado, Thomas W. Hansen, Darren C. Peets, Thomas Doert, D. S. Inosov · 发表于：Physical Review Materials · 年份：2025 · DOI：10.1103/physrevmaterials.9.033603 · 被引用次数：3 · 研究领域：Magnetic and transport properties of perovskites and related materials、Advanced Condensed Matter Physics、Multiferroics and related materials

${\mathrm{CuSn}(\mathrm{OH})}_{6}$ is a quantum spin system from the family of magnetic double perovskite hydroxides, having a frustrated magnetic sublattice. It is also known as the natural mineral mushistonite, whose crystal structure has remained elusive for decades. Here we employ x-ray and neutron powder diffraction to solve the crystal structure of ${\mathrm{CuSn}(\mathrm{OH})}_{6}$ and propose a structure model in the orthorhombic space group $Pnnn$ with correlated proton disorder. The occupation of the hydrogen sites in the structure is constrained by ``ice rules'' similar to those known for water ice, albeit with only local correlations. The resulting frustration of the hydrogen bonding network is likely to have a complex and interesting interplay with the strong magnetic frustration expected in the face-centered magnetic sublattice. Structural distortions, which are quite pronounced in ${\mathrm{Cu}}^{2+}$ compounds due to the Jahn-Teller effect, partially alleviate both types of frustration. We also show that hydrostatic pressure tends to suppress proton disorder through a sequence of proton-ordering transitions, as some of the split hydrogen sites merge already at 1.75 GPa while others show a tendency toward possible merging at higher pressures.