Tuning of electronic properties in highly lattice-mismatched epitaxial SmN

We report on the molecular beam epitaxy (MBE) growth and characterization of samarium nitride (SmN) thin films on MgO(001), focusing on the tunability of their electronic and magnetic properties via growth temperature and nitrogen flux. Despite the large lattice mismatch, all films exhibit high structural quality, confirmed by reflection high-energy electron diffraction and x-ray diffraction, with minimal strain and no secondary phases. By systematically varying the nitrogen-to-samarium ratio and substrate temperature, we demonstrate a transition from insulating to metallic behavior with carrier concentrations spanning an order of magnitude. All samples exhibit robust ferromagnetism with Curie temperatures between 27--30 K, although no superconductivity is observed down to 0.35 K, even in the most conductive samples. These findings suggest that superconductivity in SmN may be highly sensitive to carrier concentration, disorder, and interface effects. Our results provide a pathway for high-quality synthesis of SmN thin films and its potential monolithic integration of spintronic devices based on rare-earth nitride systems.