Journal of the Physical Society of Japan
Statics and Dynamics of Antiferromagnetic Ising System on a Triangular Lattice. II
和子 川崎, Tatsuya Uezu
Abstract
The Ising model on a triangular lattice with antiferromagnetic nearest neighbor and ferromagnetic next nearest neighbor interactions is investigated by treating the master equation. To terminate hierarchy structure of the equation of motion, the cluster decoupling approximation (CDA) is applied in a similar way as in the previous paper. But here, we retain not only single cumulants but also second ones. The fluctuation effect in the occurrence of the successive phase transition and “turn round” phenomena in a relaxation process are discussed. The formula of the frequency dependent susceptibility is derived within the present approximation, and the response of the system to the external oscillating field is studied. Finally, the fluctuation-dissipation theorem is derived for this spin system.