The Kosterlitz-Thouless and magnetic transition temperatures in layered magnets with a weak easy-plane anisotropy

TL;DR

This paper analyzes the magnetic phase transitions in layered 2D magnets with weak easy-plane anisotropy using renormalization group methods, deriving analytical expressions for transition temperatures that align well with experimental data.

Contribution

It provides a detailed RG analysis of the 2D Heisenberg model with easy-plane anisotropy, including two-loop corrections, offering improved predictions for transition temperatures.

Findings

Derived analytical formulas for Kosterlitz-Thouless and Curie temperatures.

Two-loop corrections improve agreement with experimental data.

Quantitative description of magnetic transitions in layered magnets.

Abstract

The two-dimensional (2D) Heisenberg magnet with a weak easy-plane anisotropy is considered. A renormalization group (RG) analysis in this model is performed for both quantum and classical cases. A crossover from the Heisenberg to 2D XY model is discussed. The magnetic transition owing to the interlayer coupling is considered. Analytical results for the Kosterlitz-Thouless and Curie (Neel) temperatures are derived with account of two-loop corrections. The results are compared with experimental data, e.g. on K2CuF4, and turn out to provide a quantitative description, unlike the standard one-loop results.