Low-temperature spin dynamics and absence of magnetic order in layered $\alpha$-RuI$_3$

TL;DR

This study reveals that $ ext{α}$-RuI$_3$ maintains dynamic spins without magnetic order down to very low temperatures, contrasting with related compounds, and exhibits two-dimensional spin fluctuations.

Contribution

The paper provides experimental evidence that $ ext{α}$-RuI$_3$ does not order magnetically and remains dynamically fluctuating at very low temperatures, unlike similar materials.

Findings

Spins in $ ext{α}$-RuI$_3$ remain dynamic down to 50 mK.

Presence of low-frequency fluctuations indicates two-dimensional spin behavior.

Contrasts with $ ext{α}$-RuCl$_3$ which shows magnetic order.

Abstract

The triangular-lattice system $\alpha$-RuI$_3$ is isostructural to the widely-studied $\alpha$-RuCl$_3$ compound which was identified as a potential Kitaev system but exhibits, instead of spin liquid behaviour, a magnetically ordered zig-zag ground state which sets in below 14~K. Here we show experimentally that, in contrast, the spins in $\alpha$-RuI$_3$ remain dynamic down to at least 50~mK. We study the spin dynamics using muon-spin relaxation methods and determine the presence of low-frequency fluctuations which are characteristic of a two-dimensional system.