Ground states of a frustrated spin-1/2 antifferomagnet: Cs_2CuCl_4 in a magnetic field

Journal article

We present detailed calculations of the magnetic ground state properties of Cs$_2$CuCl$_4$ in an applied magnetic field, and compare our results with recent experiments. The material is described by a spin Hamiltonian, determined with precision in high field measurements, in which the main interaction is antiferromagnetic Heisenberg exchange between neighboring spins on an anisotropic triangular lattice. An additional, weak Dzyaloshinkii-Moriya interaction introduces easy-plane anisotropy, so that behavior is different for transverse and longitudinal field directions. We determine the phase diagram as a function of field strength for both field directions at zero temperature, using a classical approximation as a first step. Building on this, we calculate the effect of quantum fluctuations on the ordering wavevector and components of the ordered moments, using both linear spinwave theory and a mapping to a Bose gas which gives exact results when the magnetization is almost saturated. Many aspects of the experimental data are well accounted for by this approach.

Authors: Veillette, M; Chalker, J; Coldea, R

• Publication status: Published
• Journal: Phys. Rev. B
• Volume: 71
• Issue: 21
• Pages: 214426
• Publication date: 2005-01-14
• DOI: 10.1103/PhysRevB.71.214426
• EISSN: 1550-235X
• ISSN: 1098-0121
• Language: English
• Keywords: cond-mat.stat-mech; cond-mat.str-el