Thermodynamics of anisotropic triangular magnets with ferro- and antiferromagnetic exchange
Burkhard Schmidt, Peter Thalmeier
We investigate thermodynamic properties like specific heat c V and susceptibility χ in anisotropic J 1 – J 2 triangular quantum spin systems ( ). As a universal tool we apply the finite temperature Lanczos method (FTLM) based on exact diagonalization of finite clusters with periodic boundary conditions. We use clusters up to N = 28 sites where the thermodynamic limit behavior is already stably reproduced. As a reference we also present the full diagonalization of a small eight-site cluster. After introducing model and method we discuss our main results on c V ( T ) and . We show the variation of peak position and peak height of these quantities as function of control parameter . We demonstrate that maximum peak positions and heights in Néel phase and spiral phases are strongly asymmetric, much more than in the square lattice J 1 – J 2 model. Our results also suggest a tendency to a second side maximum or shoulder formation at lower temperature for certain ranges of the control parameter. We finally explicitly determine the exchange model of the prominent triangular magnets Cs 2 CuCl 4 and Cs 2 CuBr 4 from our FTLM results.
arXiv:1506.09104•New Journal of Physics•Jul 22, 2015•37 citations