Samarium monoxide epitaxial thin film as a possible heavy-fermion compound

SmO (001) epitaxial thin films were grown on YAlO₃ (110) substrates by pulsed laser deposition method. X-ray photoemission spectroscopy indicated coexistence of Sm²⁺ and Sm³⁺, suggesting a valence fluctuating state. A SmO thin film showed a metallic conductionlike SmO polycrystal in a previous study. However, a SmO thin film showed nonmonotonical temperature dependence at low temperature in contrast with the polycrystal. A local resistivity minimum was observed at 16 K, probably caused by the dense Kondo effect, and the resistivity below 2 K was proportional to T². These features suggest the heavy-fermionic nature of SmO.