On the self-consistent spin-wave theory of layered Heisenberg magnets

TL;DR

This paper analyzes various self-consistent spin-wave theories for layered 2D Heisenberg magnets, providing analytical results for magnetization, order parameters, and critical points, and demonstrating improved agreement with experimental data through fluctuation corrections.

Contribution

It offers a comprehensive analysis of SSWT methods for layered magnets, including fluctuation corrections, enhancing the quantitative accuracy of theoretical predictions.

Findings

Analytical temperature dependence of magnetization and order parameters.

Fluctuation corrections significantly improve experimental agreement.

External magnetic field effects are incorporated into the theory.

Abstract

The versions of the self-consistent spin-wave theories (SSWT) of two-dimensional (2D) Heisenberg ferro- and antiferromagnets with a weak interlayer coupling and/or magnetic anisotropy, that are based on the non-linear Dyson-Maleev, Schwinger, and combined boson-pseudofermion representations, are analyzed. Analytical results for the temperature dependences of (sublattice) magnetization and short-range order parameter, and the critical points are obtained. The influence of external magnetic field is considered. Fluctuation corrections to SSWT are calculated within a random-phase approximation which takes into account correctly leading and next-leading logarithmic singularities. These corrections are demonstrated to improve radically the agreement with experimental data on layered perovskites and other systems. Thus an account of these fluctuations provides a quantitative theory of layered magnets.