NEW APPROACH IN THE THEORY OF LOW-DIMENSIONAL HEISENBERG MAGNETS

A new method of describing low-dimensional Heisenberg magnets with arb itrary spin is based on a generalization of Takahashi's approach. The obtained temperature dependences of the mean energy, specific heat, an d magnetic susceptibility describe the properties of the system adequa tely up to the temperatures at which the standard high-temperature exp ansion becomes valid. The main attention is devoted to the analysis of the special case of a two-dimensional antiferromagnet with spin 1/2 d escribing the magnetic subsystem of metal oxide compounds of the type La2CuO4. A comparison is made with known exact results and also with t he data of numerical experiments.