Magnetic Properties of Low Dimensional Spin Systems

Abstract

Using the method of the two-time Green's function, both static and dynamic properties of low dimensional spin systems with an anisotropic exchange interaction were investigated. It was shown that the magnetic behaviours of one- and two-dimensional spin systems are considerably different from those of the usual three-dimensional systems. That is, the transi­ tion temperature is lower than that expected from the magnitude of the coupling constant when an anisotropy is small enough. The short range order is developed more remarkably in the neighbourhood of the transition temperature. The damping constant increases in both ferro- and antiferromagnet with decreasing temperature owing to the anomalous growth of fluctuation. At the same time a broad shoulder is developed in the line shape, which may be considered as indicating quasi-collective modes of motion which persist in the paramag­ netic phase.