Chlorothionite
While the original mineral Chlorothionite K2CuSO4Cl2 was found in small quantities among the products of volcanic eruption, the synthetic "generalized" crystals of K2CuSO4Cl2-2xBr2x from our lab definitely capture attention by the size alone. On the scientific side these materials turned out to be an excellent realization of S=1/2 chain model, and continuous substitution of chlorine with bromine changes the exchange constant by almost an order of magnitude. In addition, the simple geometry of this structure allows for a rare kind of perturbation: antisymmetric Dzyaloshinskii-Moriya interaction that is uniform along the chain. Such interaction does substantially modify the quantum dynamics of the spin chain, and these model compounds offer an ideal playground for studying it.
T. A. Soldatov, A. I. Smirnov, K. Yu. Povarov, M. Hälg, W. E. A. Lorenz, and A. Zheludev, Spin gap in the quasi-one-dimensional S=1/2 antiferromagnet K2CuSO4Cl2 , external pagePhys. Rev. B 98, 144440 (2018); external pagearXiv:1810.02675
D. Blosser, N. Kestin, K. Yu. Povarov, R. Bewley, E. Coira, T. Giamarchi and A. Zheludev, Finite temperature correlations in a quantum spin chain near saturation, external pagePhys Rev B 96, 134406 (2017); external pagearXiv:1707.05243.
A. I. Smirnov, T. A. Soldatov, K. Yu. Povarov, M. Hälg, W. E. A. Lorenz, A. Zheludev, Electron spin resonance in a model S=1/2 chain antiferromagnet with a uniform Dzyaloshinskii-Moriya interaction, external pagePhys. Rev. B 92, 134417 (2015); external pagearXiv:1507.07518
M. Haelg, W. E. A. Lorenz, K. Yu. Povarov, M. Månsson, Y. Skourski and A. Zheludev, Quantum spin chains with frustration due to Dzyaloshinskii-Moriya interactions, external pagePhys. Rev. B 90, 174413 (2014); external pagearXiv:1408.5749