# Compressive-strain induced enhancement of exchange interactions and short-range magnetic order in Sr$_2$IrO$_4$ investigated by Raman spectroscopy

## TL;DR

This study demonstrates that applying compressive strain to Sr$_2$IrO$_4$ thin films enhances exchange interactions and short-range magnetic order, as shown by Raman spectroscopy and supported by density functional theory calculations.

## Contribution

It provides the first combined experimental and theoretical evidence of strain-induced enhancement of magnetic exchange interactions in Sr$_2$IrO$_4$ thin films.

## Key findings

- Two-magnon peak energy increases with compressive strain
- Enhanced magnetic interactions observed over wider temperature range
- Density functional theory confirms increased hopping and exchange with strain

## Abstract

We have carried out Raman spectroscopy experiments to investigate two-magnon excitations in epitaxial thin films of the quasi-two-dimensional antiferromagnetic Mott insulator Sr$_2$IrO$_4$ under in-plane misfit strain. With in-plane biaxial compression, the energy of the two-magnon peak increases, and the peak remains observable over a wider temperature range above the N\'eel temperature, indicating strain-induced enhancement of the superexchange interactions between $\it{J}_{eff}$ = 1/2 pseudospins. From density functional theory calculations, we have found an increase of the nearest-neighbor hopping parameter and exchange interaction with increasing biaxial compressive strain, in agreement with the experimental observations. Our experimental and theoretical results provide perspectives for systematic, theory-guided strain control of the primary exchange interactions in 5$\it{d}$ transition metal oxides.

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Source: https://tomesphere.com/paper/1908.02716