The nonlinear-σ model and its generalization on N-component spins, the O(N) model, are considered to describe thermodynamics of a quantum quasi-two-dimensional (quasi-2D) Heisenberg antiferromagnet. A comparison with standard spin-wave approaches is performed. The sublattice magnetization, Néel temperature, and spin-correlation function are calculated to first order of the 1/N expansion. A description of crossover from a 2D-like to 3D regime of sublattice magnetization temperature dependence is obtained. The values of the critical exponents derived are Β=0.36, η=0.09. An account of the corrections to the standard logarithmic term of the spin-wave theory modifies considerably the value of the Néel temperature. The thermodynamic quantities calculated are universal functions of the renormalized interlayer coupling parameter. The renormalization of the interlayer coupling parameter turns out to be considerably temperature dependent. A good agreement with experimental data on (Formula presented)(Formula presented) is obtained. The application of the approach used to the case of a ferromagnet is discussed.
|Number of pages||13|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 1997|