# Frustrated Magnetism from Local Moments in FeSe

## TL;DR

This paper models FeSe's magnetic properties using a spin-1 Heisenberg model with extended interactions, revealing a complex phase diagram and magnetic frustration that align with experimental observations.

## Contribution

It introduces a comprehensive spin model capturing FeSe's low-energy physics, highlighting magnetic frustration and multiple competing orders.

## Key findings

- Identification of a parameter regime with competing magnetic fluctuations.
- Evidence of increased magnetic frustration with temperature.
- Agreement between model predictions and experimental spin and Raman responses.

## Abstract

We investigate properties of a spin-1 Heisenberg model with extended and biquadratic interactions, which captures crucial aspects of the low energy physics in FeSe. While we show that the model exhibits a rich phase diagram with four different magnetic ordering tendencies, we identify a parameter regime with strong competition between N\`eel, staggered dimer, and stripe-like magnetic fluctuations, accounting for the physical properties of FeSe. Through the comparison of numerically evaluated spin and Raman response with experiments, we find evidence for enhanced magnetic frustration between N\`eel and co-linear stripe ordering tendencies, which increases with increasing temperature. The explanation of these spectral behaviors with this frustrated spin model supports the idea of local spin interactions in FeSe.