The quantum-spin S = 1=2 chain system Cs2CuCl4 is of high interest due to competing anti-ferromagnetic intra-chain J and inter-chain exchange J' interactions and represents a paramount example for Bose-Einstein condensation of magnons [R. Coldea et al., Phys. Rev. Lett. 88, 137202 (2002)]. Substitution of chlorine by bromine allows tuning the competing exchange interactions and corresponding magnetic frustration. Here we report on electron spin resonance (ESR) in single crystals of Cs2CuCl4−xBrx with the aim to analyze the evolution of anisotropic exchange contributions. The main source of the ESR linewidth is attributed to the uniform Dzyaloshinskii-Moriya interaction. The vector components of the Dzyaloshinskii-Moriya interaction are determined from the angular dependence of the ESR spectra using a high-temperature approximation. The obtained results support the site selectivity of the Br substitution suggested from the evolution of lattice parameters and magnetic susceptibility dependent on the Br concentration.
@article{arxiv.1905.11186,
title = {Spin relaxation in Cs$_2$CuCl$_{4-x}$Br$_x$},
author = {R. Hassan Abadi and R. M. Eremina and M. Hemmida and A. Dittl and B. Wolf and W. Assmus and A. Loidl and H. -A. Krug von Nidda},
journal= {arXiv preprint arXiv:1905.11186},
year = {2021}
}