Influences of the type of dopant and substrate on ferromagnetism in ZnO:Mn

Abstract

ZnO:Mn films doped with indium (In) and nitrogen (N) have been grown on sapphire and ZnO template substrates, respectively by the metal-organic chemical vapor deposition method. All these samples show clear hysteresis loops and saturation magnetizations (MS) at room temperature characterized by a vibrating sample magnetometer in a Quantum Design Physical Property Measurement System. For the n-type ZnO:(Mn, In) and ZnO:Mn samples, the mechanism of the room-temperature ferromagnetism (RTFM) has been ascribed to the interactions between BMPs, which are formed by the magnetic coupling between Mn ions and the oxygen vacancies (VO) defects. However, for the p-type ZnO:(Mn, N) samples, a single mechanism is not fully responsible for the measured RTFM. In contrast with the role of VO in ZnO:(Mn, In) and ZnO:Mn system, the incorporation of VO in ZnO:(Mn, N) would weaken the FM. For the ZnO:(Mn,N), the observed highest MS is mainly ascribed to the RKKY interactions from the N 2p and Mn 3d ferromagnetic exchange coupling. Besides, a density functional theory simulation also indicates that ferromagnetic coupling may be enhanced by VO in n-type ZnO:(Mn, In) and ZnO:Mn films, while the VO defects in p-type ZnO:(Mn:N) films act oppositely, that may weaken the ferromagnetic coupling.