# Critical fluctuations in the spin-orbit Mott insulator Sr$_3$Ir$_2$O$_7$

## TL;DR

This study investigates the critical magnetic fluctuations in Sr$_3$Ir$_2$O$_7$, revealing three-dimensional interactions near the Néel temperature and classifying its critical behavior within the diluted 3D Ising universality class.

## Contribution

It provides the first detailed analysis of the critical magnetic fluctuations in Sr$_3$Ir$_2$O$_7$, showing its 3D magnetic interactions and universality class, contrasting previous two-dimensional assumptions.

## Key findings

- Magnetic interactions are three-dimensional near T_N.
- Critical behavior aligns with the diluted 3D Ising universality class.
- Weak disorder influences the phase transition and critical exponents.

## Abstract

X-ray magnetic critical scattering measurements and specific heat measurements were performed on the perovskite iridate Sr$_3$Ir$_2$O$_7$. We find that the magnetic interactions close to the N\'{e}el temperature $T_N$ = 283.4(2) K are three-dimensional. This contrasts with previous studies which suggest two-dimensional behaviour like Sr$_2$IrO$_4$. Violation of the Harris criterion ($d\nu>2$) means that weak disorder becomes relevant. This leads a rounding of the antiferromagnetic phase transition at $T_N$, and modifies the critical exponents relative to the clean system. Specifically, we determine that the critical behaviour of Sr$_3$Ir$_2$O$_7$ is representative of the diluted 3D Ising universality class.