# Uniform Perpendicular and Parallel Staggered Susceptibility of Antiferromagnetic Films

## TL;DR

This paper studies the thermodynamic properties of antiferromagnetic films under perpendicular magnetic fields, calculating magnon behaviors and susceptibilities to understand spin-wave interactions at finite temperatures.

## Contribution

It provides a systematic effective Lagrangian analysis of magnon interactions and susceptibilities in antiferromagnetic films, including one-loop calculations and low-temperature series.

## Key findings

- Magnon dispersion relations derived up to one-loop order.
- Separation of free energy into noninteracting and interacting magnon contributions.
- Analysis of low-temperature susceptibilities and the impact of magnon interactions.

## Abstract

We investigate the thermodynamic behavior of antiferromagnetic films in external magnetic fields oriented perpendicular to the staggered magnetization. Within the systematic effective Lagrangian framework we first calculate the two-point function and the dispersion relation for the two types of magnons up to one-loop order. This allows us to split the two-loop free energy density into a piece that originates from noninteracting dressed magnons, and a second piece that corresponds to the genuine magnon-magnon interaction. We then discuss the low-temperature series for various thermodynamic quantities, including the parallel staggered and uniform perpendicular susceptibilities, and analyze the role of the spin-wave interaction at finite temperature.