Interfacial structure and magnetic coupling at Fe3O4/FeO (001) and (111) interfaces

Heterointerfaces between ferromagnetic and antiferromagnetic materials play an important role in the development and applications of magnetic and electronic devices. Here, atomic and electronic structures of two types of Fe₃O₄/FeO interfaces with different magnetic coupling modes have been investigated by combining advanced transmission electron microscopy and first-principles calculations. It is found that the Fe₃O₄/FeO (001) and Fe₃O₄/FeO (111) interfaces can be formed between FeO and Fe₃O₄ due to different phase transformations. The Fe₃O₄/FeO (111) interface is generally closer to the steady state. The electronic structure of both types of Fe₃O₄/FeO interfaces changes significantly, which leads to a metal-insulator transition of the Fe₃O₄ layer at the interfaces. The energy difference between the ferromagnetic and antiferromagnetic coupling states across the Fe₃O₄/FeO interfaces is very small, indicating that magnetic flip-flopping easily occurs in the Fe₃O₄/FeO system. The atomic magnetic moment of the interfacial Fe atoms at the Fe₃O₄/FeO (001) interface decreases by {~}10% due to the preferentially occupied dxz and dyz orbitals, while that at the Fe₃O₄/FeO (111) interface remains almost unchanged. These findings suggest that the Fe₃O₄/FeO interfaces are susceptible to magnetic coupling transition and may find applications in low-power consumption magnetic and electronic devices.