TEMPERATURE-DEPENDENCE OF THE MAGNETIC-SUSCEPTIBILITY OF THE SPIN 1 2ANTIFERROMAGNETIC XXZ MODEL ON A SQUARE LATTICE/

The magnetic susceptibility of the XXZ model is studied over a wide te mperature range by the Green's function method with the Kondo-Yamaji d ecoupling scheme. By this method it is possible that both XY- and Isin g-like systems are studied in a unified way. In the XY-like system, ou r results of the transverse uniform susceptibility agree with those of a Monte-Carlo simulation. In the Ising-like system, our temperature d ependence of the longitudinal uniform susceptibility agrees well with the experimental results of the susceptibility of quasi-2D Ising-Like antiferromagnet K2CoF4 above its Neel point.