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TT: Fachverband Tiefe Temperaturen
TT 49: CE: Spin Systems and Itinerant Magnets 2
TT 49.10: Talk
Thursday, March 17, 2011, 16:30–16:45, HSZ 03
Derivation of effective microscopic models for the frustrated antiferromagnets Cs2CuCl4 and Cs2CuBr4 from first principles — •Kateryna Foyevtsova, Ingo Opahle, Yu-Zhong Zhang, Harald O. Jeschke, and Roser Valentì — Institut für Theoretische Physik, Goethe-Universität Frankfurt, 60438 Frankfurt am Main, Germany
We report on the density functional theory (DFT) investigations of the frustrated triangular-lattice antiferromagnets Cs2CuCl4 and Cs2CuBr4, which in particular focus on derivation of effective models for the two compounds. The drastic disagreement between the Heisenberg model that we derived for Cs2CuCl4 using its X-ray structural data and the experimentally established model motivated us to perform a detailed study of the crystal structure optimization effects on the exchange couplings with a number of exchange-correlation functionals for Cs2CuCl4 as well as for Cs2CuBr4. We find that, in order to obtain results that are consistent with experiment, one has to consider during the optimization an insulating state, appearing only with a spin-polarized exchange-correlation functional, and electronic correlations (within the LDA+U approach). We will in addition discuss the effect of interlayer couplings as well as longer-ranged couplings in both systems.
As the mixed Cs2CuCl4−xBrx (0<x<4) systems have been gaining a lot of attention recently, we also present some DFT insights on the distribution of either of the halide atoms at various mixing factors.