Spin correlations and Dzyaloshinskii-Moriya interaction in Cs2CuCl4

Abstract

We report on electron spin resonance (ESR) studies of the spin relaxation in Cs2CuCl4. The main source of the ESR linewidth at temperatures T ≤ 150 K is attributed to the uniform DzyaloshinskiiMoriya interaction. The vector components of the Dzyaloshinskii-Moriya interaction are determined from the angular dependence of the ESR spectra using a high-temperature approximation. Both the angular and temperature dependence of the ESR linewidth have been analyzed using a selfconsistent quantum-mechanical approach. In addition analytical expressions based on a quasiclassical picture for spin fluctuations are derived, which show good agreement with the quantumapproach for temperatures T ≥ 2J/kB ≈ 15 K. A small modulation of the ESR linewidth observed in the ac-plane is attributed to the anisotropic Zeeman interaction, which reflects the two magnetically nonequivalent Cu positions.

Quantum spin chains with frustration due to Dzyaloshinskii-Moriya interactions

“…Electron spin resonance (ESR) was recently predicted [33] and experimentally demonstrated [34,35] to be a sensitive probe for DM interactions in spin chain systems. In the presence of DM interactions the excitation spectrum of the spin chain is shifted along the spinon propagation direction and develops a corresponding gap at zero momentum transfer.…”

Direct Determination of Exchange Parameters inCs2CuBr4andCs2<

“…So far, experiments on CCC gave estimates for three DM parameters: D a 0 =J ∼ 5% [8] and D a;c =J ∼ 10% [25,28]. The reduced translational symmetry of the copper layers in CCC (CCB) revealed by the staggered DM vectors (3) leads to the folding of the Brillouin zone of a simple triangular Bravais lattice.…”

EPR studies of the triangular-lattice antiferromagnet Cs2CuBr4

“…and c, respectively. It is important to mention, that contrary to many other spin-1/2 exchange-coupled spin systems with spin interactions of the same order of magnitude [20][21][22][23], the high-temperature EPR line in Cs 2 CuBr 4 is up to two orders of magnitude broader (for comparison, the EPR linewidth in the isostructural compound Cs 2 CuCl 4 measured at T = 100 K is ~0.02-0.03 T [17], which is about 50 times smaller than the EPR linewidth in Cs 2 CuBr 4 ). Let us discuss possible contributions, which affect the EPR linewidth.…”

“…Electron paramagnetic resonance (EPR, also known as electron spin resonance, ESR) spectroscopy is recognized as a very powerful tool to probe the anisotropy of magnetic interactions in strongly correlated spin systems. Recently performed EPR studies of Cs 2 CuCl 4 [17] provided the important information on the magnetic anisotropy in this material. It was shown that the main source of the hightemperature EPR line broadening is the Dzyaloshinskii-Moriya (DM) interaction.…”