Temperature dependence of the magnetic susceptibility for triangular-lattice antiferromagnets with spatially anisotropic exchange constants

Weihong Zheng, Rajiv R. P. Singh, Ross H. McKenzie, Radu Coldea
2005 Physical Review B  
We present the temperature dependence of the uniform susceptibility of spin-half quantum antiferromagnets on spatially anisotropic triangular-lattices, using high temperature series expansions. We consider a model with two exchange constants, J_1 and J_2 on a lattice that interpolates between the limits of a square-lattice (J_1=0), a triangular-lattice (J_2=J_1), and decoupled linear chains (J_2=0). In all cases, the susceptibility which has a Curie-Weiss behavior at high temperatures, rolls
more » ... r and begins to decrease below a peak temperature, T_p. Scaling the exchange constants to get the same peak temperature, shows that the susceptibilities for the square-lattice and linear chain limits have similar magnitudes near the peak. Maximum deviation arises near the triangular-lattice limit, where frustration leads to much smaller susceptibility and with a flatter temperature dependence. We compare our results to the inorganic materials Cs_2CuCl_4 and Cs_2CuBr_4 and to a number of organic molecular crystals. We find that the former (Cs_2CuCl_4 and Cs_2CuBr_4) are weakly frustrated and their exchange parameters determined through the temperature dependence of the susceptibility are in agreement with neutron-scattering measurements. In contrast, the organic materials are strongly frustrated with exchange parameters near the isotropic triangular-lattice limit.
doi:10.1103/physrevb.71.134422 fatcat:cyhyla36angkdkfnf73fd2xz5u