2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/21119In the paper we describe the modification of self-consistent harmonic approximation for quantum S=1 systems. This method has a number of advantages in comparison with usual SCHA. We apply the method to two-dimensional ferromagnets with easy-axis exchange or single-site anisotropy. The results are in good agreement with Monte-Carlo simulations and pure-quantum SCHA.15 pages, 2 figures Some mistakes have been correctedStrongly Correlated Electronstext