Reconfigurable phase in manganese nitride thin films by nitrogen stoichiometry

Transition-metal nitrides exhibit excellent electrical conductivity, chemical stability, and diverse physical properties, making them promising for GaN-based semiconductors, quantum bits, and spintronic applications. However, precise and reversible control of nitrogen stoichiometry for nitrides remains scarce and challenging. Here, we present a two-step annealing strategy to modulate nitrogen content in manganese nitride thin films. By combining in situ vacuum annealing and rapid thermal annealing in ammonia, reversible phase transitions between antiferromagnetic θ-MnN and ferrimagnetic ε-Mn4N are achieved, accompanied by a switch in the dominant carrier type from electron-like to hole-like and the emergence of a square-shaped anomalous Hall hysteresis loop. These results demonstrate that nitrogen stoichiometry serves as an effective and reversible parameter for tuning structural, electronic, and magnetic properties, providing a feasible pathway for phase engineering in transition-metal nitrides and enabling potential applications in reconfigurable spintronic devices.