CPX
Copper pyrydine halogenides are well-established examples of the spin chain materials. The "end" compounds with x=0 or 1 (corresponding to pure chlorine or bromine composition) may serve as the nice subjects to probe the exotic chain physics, but the significance of this particular family is larger than that. The possibility of having the mixed composition opens the route for studying the spin chains in the presence of bond disorder. In principle, this may lead to novel quantum collective states, such as the Random Singlet Phase.
J. Zeisner, M. Brockmann, S. Zimmermann, A. Weiße, M. Thede, E. Ressouche, K. Yu. Povarov, A. Zheludev, A. Klümper, B. Büchner, V. Kataev, F. Göhmann, Anisotropic magnetic interactions and spin dynamics in the spin chain compounds Cu(py)2(Cl1-xBrx)2 (x = 1.0, 0.98, 0.95): An experimental and theoretical study, external pagePhys. Rev. B 96, 024429 (2017); external pagearXiv:1704.05705
A. N. Ponomaryov, L. Zviagina, J. Wosnitza, M. Thede, E. Ressouche, K. Yu. Povarov, A. Zheludev, C. P. Landee, and S. A. Zvyagin, Low-temperature magnetic structure and electron paramagnetic resonance properties of the quasi-one-dimensional S=1/2 Heisenberg helimagnet CuCl2-2NC5H5, external pagePhys. Rev. B 95, 195125 (2017)
M. Thede, F. Xiao, Ch. Baines, C. Landee, E. Morenzoni, A. Zheludev, Ordering in weakly coupled random singlet spin chains, external pagePhys. Rev. B 86, 180407(R) (2012); external pagearXiv:1208.6479v1