Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 29: Correlated Electrons: Low-dimensional Systems - Materials 2
TT 29.13: Vortrag
Mittwoch, 25. März 2009, 17:30–17:45, HSZ 301
Understanding magnetic properties of layered copper oxychloride (CuCl)LaNb2O7 — •Alexander Tsirlin1,2 and Helge Rosner1 — 1Max-Planck Institute CPfS, Dresden, Germany — 2Department of Chemistry, MSU, Moscow, Russia
The copper-containing oxychloride (CuCl)LaNb2O7 is one of the actively studied low-dimensional spin systems. Experimental data evidence the strong frustration of this compound, but the microscopic scenario of the frustration remains unknown. Initially, (CuCl)LaNb2O7 was considered as a promising realization of the spin-1/2 frustrated square lattice model. However, further studies suggested the sizable structural distortion, leading to a more complex spin physics. Experimental techniques fail to resolve the distorted structure, hence impeding the understanding of the magnetic properties. In this contribution, we present a computational study of (CuCl)LaNb2O7 and propose a valid miscroscopic scenario that accounts for all the experimental data available so far. Our results indicate orbital degeneracy as a primary origin of the structural distortion. The distorted structure is orthorhombic and includes CuO2Cl2 plaquettes instead of CuO2Cl4 octahedra in the regular structure. The distortion strongly modifies the exchange couplings in (CuCl)LaNb2O7 and leads to a three-dimensional spin model with pronounced one-dimensional features. Our findings propose a general scenario for the structural distortion and the spin physics of (CuX)LaM2O7 (X = Cl, Br; M = Nb, Ta) as well as an outlook for further experimental studies of these compounds.