Electronic Structure and Ferromagnetism Modulation in Cu/Cu₂O Interface: Impact of Interfacial Cu Vacancy and Its Diffusion

摘要

Cu/Cu₂O composite structures have been discovered to show sizable ferromagnetism (FM) with the potential applications in spintronic devices. To date, there is no consensus on the FM origin in Cu/Cu₂O systems. Here, first principles calculations are performed on the interface structure to explore the microscopic mechanism of the FM. It is found that only the Cu vacancy (V_Cu) adjacent to the outermost Cu₂O layer induces a considerable magnetic moment, mostly contributed by 2 p orbitals of the nearest-neighbor oxygen atom (O_NN) with two dangling bonds and 3 d orbitals of the Cu atoms bonding with the O_NN. Meanwhile, the charge transfer from Cu to Cu₂O creates higher density of states at the Fermi level and subsequently leads to the spontaneous FM. Furthermore, the FM could be modulated by the amount of interfacial V_Cu, governed by the interfacial Cu diffusion with a moderate energy barrier (~1.2?eV). These findings provide insights into the FM mechanism and tuning the FM via interfacial cation diffusion in the Cu/Cu₂O contact.