Locallized Magnetism in Low-Dimensional Systems

TL;DR

This paper reviews the magnetic properties of low-dimensional insulating systems, highlighting the limitations of traditional theories and discussing advanced field-theoretical approaches that better match experimental observations.

Contribution

It introduces analytical expressions for magnetic transition temperatures and order parameters that align well with experimental data, advancing understanding of low-dimensional magnetism.

Findings

Standard and self-consistent spin-wave theories are insufficient.

Field-theoretical approaches improve agreement with experiments.

Analytical formulas for $T_M$ and order parameters are derived.

Abstract

The current theoretical and experimental situation is reviewed for low-dimensional (layered and chain-like) insulating systems. Such systems possess a low magnetic transition temperature $T_M$ and pronounced short-range magnetic order above this temperature. Both the standard and self-consistent spin-wave theories are shown to be insufficient to quantitatively describe the experimental data on these systems. Field-theoretical approaches taking into account the contribution of the spin-fluctuation excitations (neglected in the spin-wave theories) to the thermodynamic properties of ferro- and antiferromagnets are discussed. Analytical expressions for $T_M$ and temperature dependences of long-range order paramenters are obtained, which are in a fair agreement with experimental data.