Measuring Thermal Conductivity of NdNiO₃ Thin Films with Frequency Domain Thermoreflectance

NdNiO₃ has attracted attention for its concomitant, thermally-driven metal-insulator and magnetic ordering transitions. This metal-insulator transition is particularly interesting in thin film form, as it can be tuned using epitaxial strain and rare-earth doping [1]. Understanding the thermal conductivity in these NdNiO₃ films is necessary before using them in devices or exploring their applications in electronics like thermal transistors or switches. This fundamental understanding of heat transport can illuminate both electron and phonon behavior in these films. Here, we synthesize NdNiO₃ films using molecular beam epitaxy (MBE) to create high-quality thin films. We then use frequency-domain thermoreflectance (FDTR) measurements to non-destructively determine the thermal conductivity of NdNiO₃ films across the metal-insulator transition [2]. Using FDTR, we observe the low-temperature (~100K) metal-insulator phase transition of NdNiO₃ and its hysteresis by measuring thermal conductivity as a function of temperature. We analyze our thermal conductivity data in connection with previous research into the electronic properties of NdNiO₃.<br/>[1] Zhang, J., Kim, H., Mikheev, E. et al. Key role of lattice symmetry in the metal-insulator transition of NdNiO₃ films. Sci Rep 6, 23652 (2016).<br/>[2] Schmidt, A., Cheaito, R., Chiesa, M. A frequency-domain thermoreflectance method for the characterization of thermal properties. Rev. Sci. Instrum. 1, 094901 (2009).