Browsing by Author "Pomjakushin, Vladimir Yu."

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Open Access
Data Underpinning: Correlated proton disorder in the crystal structure of the double hydroxide perovskite CuSn(OH)₆
(Technische Universität Dresden, 2025-01-16) Peets, Darren Campbell; Kulbakov, Anton A.; Häußler, Ellen; Parui, Kaushick K.; Mannathanath Chakkingal, Aswathi; Pavlovskii, Nikolai S.; Pomjakushin, Vladimir Yu.; Cañadillas-Delgado, Laura; Hansen, Thomas; Doert, Thomas; Inosov, Dmytro S.
This contains the data underpinning our paper on CuSn(OH)₆. The abstract of the article is reproduced here: CuSn(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 CuSn(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. 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-centred magnetic sublattice. Structural distortions, which are quite pronounced in Cu2+ 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.
Open Access
Data Underpinning: Spin Liquid Mimicry in the Hydroxide Double Perovskite CuSn(OD)₆ Induced by Correlated Proton Disorder
(Technische Universität Dresden, 2025-06-26) Kulbakov, Anton A.; Häußler, Ellen; Parui, Kaushick K.; Pavlovskii, Nikolai S.; Mannathanath Chakkingal, Aswathi; Granovsky, Sergey A.; Gaß, Sebastian; Corredor Bohórquez, Laura Teresa; Wolter, Anja U. B.; Zvyagin, Sergei A.; Skourski, Yurii V.; Pomjakushin, Vladimir Yu.; Puente-Orench, Inés; Peets, Darren Campbell; Doert, Thomas; Inosov, Dmytro. S.
The face-centered-cubic lattice is composed of edge-sharing tetrahedra, making it a leading candidate host for strongly frustrated magnetism, but relatively few face-centered frustrated materials have been investigated. In the hydroxide double perovskite CuSn(OH)6, magnetic frustration of the Cu2+ quantum spins is partially relieved by strong Jahn-Teller distortions. Nevertheless, the system shows no signs of long-range magnetic order down to 45 mK and instead exhibits broad thermodynamic anomalies in specific heat and magnetization, indicating short-range dynamical spin correlations — a behavior typical of quantum spin liquids. We propose that such an unusual robustness of the spin-liquid-like state is a combined effect of quantum fluctuations of the quantum spins S = 1/2 , residual frustration on the highly distorted face-centered Cu2+ sublattice, and correlated proton disorder. Similar to the disorder-induced spin-liquid mimicry in YbMgGaO4 and herbertsmithite, proton disorder destabilizes the long-range magnetic order by introducing randomness into the magnetic exchange interaction network. However, unlike the quenched substitutional disorder on the magnetic sublattice, which is difficult to control, proton disorder can in principle be tuned through pressure-driven proton ordering transitions. This opens up the prospect of tuning the degree of disorder in a magnetic system to better understand its influence on the magnetic ground state.