Thermodynamics of anisotropic triangular magnets with ferro- and antiferromagnetic exchange

Burkhard Schmidt; Peter Thalmeier

doi:10.1088/1367-2630/17/7/073025

paper

Thermodynamics of anisotropic triangular magnets with ferro- and antiferromagnetic exchange

arXiv:1506.09104 · doi:10.1088/1367-2630/17/7/073025

Abstract

We investigate thermodynamic properties like specific heat $c_{V}$ and susceptibility $χ$ in anisotropic $J_{1}$ - $J_{2}$ triangular quantum spin systems ( $S = 1/2$ ). 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 $χ (T)$ . We show the variation of peak position and peak height of these quantities as function of control parameter $J_{2} / J_{1}$ . 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.

13 pages, 12 figures

Thermodynamics of anisotropic triangular magnets with ferro- and antiferromagnetic exchange

Abstract

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