Quantitative Description of Thermodynamics of Layered Magnets in a Wide Temperature Region

The thermodynamics of layered antiferro- and ferromagnets with a weak interlayer coupling and/or easy-axis anisotropy is investigated. A crossover from an isotropic 2D-like to 3D Heisenberg (or 2D Ising) regime is discussed within the renormalization group (RG) analysis. Analytical results for the the (sublattice) magnetization and the ordering temperature are derived are obtained in different regimes. Numerical calculations on the base of the equations obtained yield a good agreement with experimental data on La2CuO4 and layered perovskites. Corresponding results for the Kosterlitz-Thouless and Curie (N\'eel) temperatures in the case of the easy-plane anisotropy are derived.