SPONTANEOUS STAGGERED MAGNETIZATION IN ANTIFERROMAGNETIC HEISENBERG-ISING CHAINS

We calculate numerically the spontaneous staggered magnetization and s usceptibility of the ground state of quantum antiferromagnetic Heisenb eg-Ising chains. We use a zero-temperature Monte Carlo method and cons ider the cases of spin 1 and 2. As a function of the anisotropy parame ter, the magnetization vanishes continuously at a critical point whose critical exponents for both cases are found to be in agreement with t hose of the two-dimensional Ising model.