INVESTIGATION OF THE HYPERFINE INTERACTION IN THE ANTIFERROMAGNETIC CSMNI3

The lower branch of the resonance spectrum of the quasi-one-dimensiona l triangular antiferromagnetic CsMnI3 has been investigated experiment ally. This branch possesses a gap due to the dynamic hyperfine interac tion. The temperature dependence of the energy gap was studied in deta il at several frequencies. A theoretical calculation of the correspond ing spectrum of coupled electron-nuclear spin oscillations was perform ed in the ''hydrodynamic approximation'' with an empirical correction for thermal fluctuations of the antiferromagnetic system. The good agr eement between the calculation and experimental data makes it possible to determine the zero-point spin reduction in the antiferromagnetic. (C) 1997 American Institute of Physics.