Thermal conductivity and specific heat in exfoliated magnets: α-RuCl3 and FePS3.

Thermal transport in two-dimensional magnets remains poorly understood. Here we extend the 3ω technique which is commonly used for bulk materials, to suspended flakes of layered materials, enabling simultaneous extraction of specific heat and in-plane thermal conductivity. In FePS₃, our measurements reveal a clear peak in the specific heat at ~120 K with a concomitant rise in the thermal conductivity to lower temperatures, consistent with the antiferromagnetic transition. We further investigate the thermal response of the Kitaev magnet α-RuCl₃ and find it at odds with the bulk transport behavior, suggesting a sensitivity to disorder from exfoliation and/or fabrication. Our results demonstrate that 3ω measurements of suspended samples are a viable means to probe the thermal properties of 2D magnets.