Single-molecule spin devices: Fundamentals, advances, and prospects

Single-molecule spintronics is an emerging interdisciplinary field that integrates molecular electronics with spin-based information science, offering novel pathways for encoding, manipulating, and detecting spin at the molecular level. This review explores the fundamental principles, advances, and prospects of single-molecule spin devices, emphasizing the manipulation of spin states in various molecular systems, such as single-molecule magnets, spin crossover complexes, organic radicals, and chiral molecules. Due to their intrinsic quantum characteristics and tunable functionalities, these systems serve as ideal platforms for investigating spin-related phenomena including Kondo effects, spin filtering, and thermoelectric effects. The integration of molecular junctions with advanced measurement techniques, such as spin-polarized scanning tunneling microscopy and electron spin resonance, has significantly advanced the understanding of spin transport and coherence in single-molecule configurations. Furthermore, potential applications of these molecules in devices like spin valves, spin switches, and quantum bits are discussed, highlighting their promise for realizing low-power, high-efficiency spintronic technologies. Despite significant progress, several challenges remain in terms of stability, reproducibility, and scalability, necessitating further research into molecular design, interfacial engineering, and quantum coherence to enable practical applications in molecular spintronics and quantum information science.