The two-dimensional frustrated Heisenberg model on the orthorhombic lattice

TL;DR

This paper analyzes high-field magnetization data for layered vanadium phosphates using a frustrated Heisenberg model on an orthorhombic lattice, showing good agreement with experiments and discussing implications for magnetic frustration in related compounds.

Contribution

It extends the square-lattice Heisenberg model to an orthorhombic lattice and compares theoretical predictions with experimental data, highlighting the model's robustness despite lower symmetry.

Findings

Predictions for saturation fields match experimental data.

The magnetization curves below saturation agree with experiments.

The orthorhombic model explains magnetic susceptibility behavior.

Abstract

We discuss new high-field magnetization data recently obtained by Tsirlin et al. for layered vanadium phosphates in the framework of the square-lattice model. Our predictions for the saturation fields compare exceptionally well to the experimental findings, and the strong bending of the curves below saturation agrees very well with the experimental field dependence. Furthermore we discuss the remarkably good agreement of the frustrated Heisenberg model on the square lattice in spite of the fact that the compounds described with this model actually have a lower crystallographic symmetry. We present results from our calculations on the thermodynamics of the model on the orthorhombic (i.e., rectangular) lattice, in particular the temperature dependence of the magnetic susceptibility. This analysis also sheds light on the discussion of magnetic frustration and anisotropy of a class of iron pnictide parent compounds, where several alternative suggestions for the magnetic exchange models were proposed.