Sample thickness dependence of structural and magnetic properties in $\alpha$-RuCl$_3$

TL;DR

This study investigates how the structural and magnetic properties of $ ext{α-RuCl}_3$ vary with sample thickness, revealing that thinner samples and cleaving influence magnetic transitions and structural phases, with implications for understanding sample quality effects.

Contribution

The paper introduces a non-destructive exfoliation protocol for $ ext{α-RuCl}_3$ and demonstrates how sample thickness affects magnetic and structural transitions, especially in low-quality or small samples.

Findings

Magnetic features at 10 K/12 K emerge with cleaving.

Sample quality improves with successive cleaving.

Persistence of C2/m structure correlates with magnetic anomalies.

Abstract

The layered transition metal trihalide $\alpha$-RuCl$_3$ has been studied extensively in recent years as a promising candidate for a proximate Kitaev quantum spin liquid state. In high quality samples, a complete structural transition from room-temperature C2/m to low-temperature R$\bar{3}$ is consistently observed, with a single magnetic transition to antiferromagnetic ordering at $\sim$7K. However, magnetic and physical properties have been shown to depend heavily on both sample size and sample quality, with small and damaged samples exhibiting incomplete structural transitions and multiple magnetic anomalies. Although large high quality samples have been well studied, an understanding of the features attributed to low quality or small sample size is limited. Here, we probe the structural and magnetic transitions of $\alpha$-RuCl$_3$ single crystal samples via magnetic susceptibility through a range of thickness, manipulated through careful mechanical exfoliation. We present a non-destructive protocol for exfoliating crystals and show success to 30 $\mu$m, where sample quality is observed to improve with successive cleaving. Higher temperature magnetic features at 10 K/12 K are found to emerge through cleaving, both with and without induced sample damage. In both cases, we link these additional magnetic features to a persistence of C2/m structure to the low-temperature regime.