# Magneto‐Structural Properties of the Layered Quasi‐2D Triangular‐Lattice Antiferromagnets Cs2CuCl4−xBrx for x = 0, 1, 2, and 4

Published on Sep 1, 2019in Physica Status Solidi B-basic Solid State Physics1.454

· DOI :10.1002/pssb.201900044

Abstract

We present a study of the magnetic susceptibility \chi_{mol}under variable hydrostatic pressure on single crystals of Cs_2uCl_{4-x}r_x This includes the border compounds \textit{x} = 0 and 4, known as good realizations of the distorted triangular-lattice spin-1/2 Heisenberg antiferromagnet, as well as the isostructural stoichiometric systems Cs_2uCl_{3}r_1and Cs_2uCl_{2}r_2 For the determination of the exchange coupling constants Jand J^{\prime} \chi_{mol}data were fitted by a J-J^{\prime}model \cite{Schmidt2015}. Its application, validated for the border compounds, yields a degree of frustration J^{\prime}J= 0.47 for Cs_2uCl_3r_1and J^{\prime}J\simeq0.63 - 0.78 for Cs_2uCl_2r_2 making these systems particular interesting representatives of this family. From the evolution of the magnetic susceptibility under pressure up to about 0.4\,GPa, the maximum pressure applied, two observations were made for all the compounds investigated here. First, we find that the overall energy scale, given by J_c = (J^2+ J^{\prime 2}^{1/2} increases under pressure, whereas the ratio J^{\prime}Jremains unchanged in this pressure range. These experimental observations are in accordance with the results of DFT calculations performed for these materials. Secondly, for the magnetoelastic coupling constants, extraordinarily small values are obtained. We assign these observations to a structural peculiarity of this class of materials.