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

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.