EFFECT OF THE MAGNETIC-FIELD ON QUANTUM FLUCTUATIONS IN QUASI-ONE-DIMENSIONAL HEXAGONAL ANTIFERROMAGNETS

Effect of zero-point spin motion on the ground-state properties of quasi-one-dimensional antiferromagnets CsNiCl3 and CsMnBr3 is considered. Comparison of the low-temperature magnetization curves measured in these compounds with the results of spin-wave calculations reveals two principal features: (1) The measured magnetic torques are strongly reduced with respect to the values calculated in classical approximation due to zero-point spin oscillations. This is found to be in a good agreement with the neutron scattering results. The value of the spin reduction at H = 0 appears to be well reproduced by the harmonic approximation of the routine spin-wave theory. (2) Strongly nonlinear growth of the magnetization with magnetic field is observed. It can be regarded as a direct evidence for the gradual supression of quantum fluctuations by the increasing magnetic field.