Theoretical Study of Magnetic Properties of Singlet-Ground-State System RbFeCl3

Magnetic properties in the paramagnetic phase of pseudo-one-dimensional singlet-ground-state system RbFeCl 3 are studied by taking into account interchain coupling. Calculations are performed on the basis of three different approximations, dynamical correlated-effective-field approximation (D-CEFA) with single correlation parameter, D-CEFA with two correlation parameters, and static CEFA (S-CEFA). Among them D-CEFA with single correlation parameter explains most reasonably various magnetic properties such as the Néel temperature, the magnon dispersion, the temperature and magnetic-field ( H // c -axis) dependence of the magnon energies, and the field dependence of the Néel temperature. The ratio of the interchain coupling to the intrachain coupling is determined to be ∼0.1, which indicates poor one-dimensionality of RbFeCl 3 .