Browsing by Author "Parui, Kaushick K."

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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.
Open Access
Data Underpinning: Disorder-driven magnetic duality in the spin-½ system ktenasite, Cu₂.₇Zn₂.₃(SO₄)₂(OH)₆·6H₂O
(Technische Universität Dresden, 2025-10-17) Parui, Kaushick K.; Kulbakov, Anton A.; Gumeniuk, Roman; Carrillo-Aravena, Eduardo; Fernández-Díaz, María Teresa; Savvin, Stanislav; Korshunov, Artem; Granovsky, Sergey; Doert, Thomas; Inosov, Dmytro S.; Peets, Darren C.
Article abstract: Disorder in frustrated quantum systems can critically influence their magnetic ground states and drive exotic magnetic behavior. In the S = ½ system ktenasite, Cu₂.₇Zn₂.₃(SO₄)₂(OH)₆·6H₂O, we show that structural disorder drives an unexpected dimensional crossover and stabilizes a rare coexistence of distinct magnetic states. Neutron diffraction reveals significant Cu/Zn mixing at the Cu2 site, which tunes the Cu²⁺ sublattice from a two-dimensional scalene-distorted triangular lattice into a one-dimensional spin-chain network. Magnetic susceptibility, neutron diffraction, ac susceptibility, and specific heat measurements collectively indicate magnetic duality: a coexistence of incommensurate long-range magnetic order below TN = 4 K and a cluster spin-glass state with Tf = 3.28 K at f = 10 Hz. Our findings highlight ktenasite as a rare platform where structural disorder tunes the effective dimensionality and stabilizes coexisting ordered and glassy magnetic phases, offering a unique opportunity to explore the interplay of frustration, disorder, and dimensional crossover in quantum magnets.
Open Access
Data Underpinning: Disordered ground state in the 3D face-centred frustrated spin-5/2 system MnSn(OH)₆
(Technische Universität Dresden, 2025-03-04) Parui, Kaushick K.; Kulbakov, Anton A.; Häußler, Ellen; Pavlovskii, Nikolai S.; Mannathanath Chakkingal, Aswathi; Avdeev, Maxim; Gumeniuk, Roman; Granovsky, Sergey; Mistonov, Alexander; Zvyagin, Sergei; Doert, Thomas; Inosov, Dmytro S.; Peets, Darren C.
This contains the data underpinning our paper on MnSn(OH)₆. The abstract of the article is reproduced below: Frustrated magnetism in face-centered cubic (fcc) magnetic sublattices remains underexplored but holds considerable potential for exotic magnetic behavior. Here, we report on the crystal structural, magnetic and thermodynamic properties of the A-site-vacant double hydroxide perovskite MnSn(OH)₆. Despite dominant antiferromagnetic interactions among Mn²⁺ moments, evidenced by a negative Curie-Weiss temperature, the lack of a sharp thermodynamic transition down to 350 mK implies the absence of long-range magnetic order. However, a broad hump at 1.6 K suggests short-range correlations and spin freezing, with power-law behavior consistent with a spin-glass state. Neutron diffraction at low temperatures confirms the presence of three-dimensional (3D) antiferromagnetic correlations, manifesting as diffuse magnetic scattering with a correlation length ξ = 24.66 Å and a magnetic propagation vector k = (0 0 ½) at 20 mK.
Open Access
Data Underpinning: Stacking Disorder in Novel ABAC-Stacked Brochantite, Cu₄SO₄(OH)₆
(Technische Universität Dresden, 2025-01-16) Mannathanath Chakkingal, Aswathi; Fuller, Chloe; Avdeev, Maxim; Gumeniuk, Roman; Parui, Kaushick K.; Rahn, Marein C.; Pabst, Falk; Wang, Yiran; Granovsky, Sergey; Korshunov, Artem; Chernyshov, Dmitry; Inosov, Dmytro S.; Peets, Darren C.
Abstract of the accompanying article: In geometrically frustrated magnetic systems, weak interactions or slight changes to the structure can tip the delicate balance of exchange interactions, sending the system into a different ground state. Brochantite, Cu₄SO₄(OH)₆, has a copper sublattice composed of distorted triangles, making it a likely host for frustrated magnetism, but exhibits stacking disorder. The lack of synthetic single crystals has limited research on the magnetism in brochantite to powders and natural mineral crystals. We grew crystals which we find to be a new polytype with a tendency toward ABAC stacking and some anion disorder, alongside the expected stacking disorder. Comparison to previous results on natural mineral specimens suggests that cation disorder is more deleterious to the magnetism than anion and stacking disorder. Our specific heat data suggest a double transition on cooling into the magnetically ordered state.