New approach in the theory of low-dimensional Heisenberg magnets

A new method of describing low-dimensional Heisenberg magnets with arbitrary spin is based on a generalization of Takahashi's approach. The obtained temperature dependences of the mean energy, specific heat, and magnetic susceptibility describe the properties of the system adequately up to the temperatures at which the standard high-temperature expansion becomes valid. The main attention is devoted to the analysis of the special case of a two-dimensional antiferromagnet with spin $1/2$ describing the magnetic subsystem of metal oxide compounds of the type La$_2$CuO$_4$. A comparison is made with known exact results and also with the data of numerical experiments.