ESR Modes in CsCuCl₃

Abstract

The ESR Modes in CsCuCl₃ are calculated using a model of spins forming a helix with a long period along the c-axis due to the Dzyaloshinsky-Moriya interaction and a 120° structure in the c-plane due to the antiferromagnetic interaction on the triangular lattice. For the case of the external field H parallel to the c-axis the resonance condition for the two observable modes is approximately
ω_±⁄γ={3H_E1(H²_DM⁄H_E0+H_A)+(H⁄2)²}^1⁄2±H⁄2,
whereas the third mode is a zero mode. H_E0 and H_E1 are the intrachain and interchain exchange fields, H_DM and H_A are the effective fields due to the Dzyaloshinsky-Moriya interaction and the anisotropy in the exchange interaction. The frequency versus field diagram is in good agreement with the experimental findings of Palme et al., however our analysis is different from theirs in order to be compatible with the neutron scattering results of Adachi et al.