Ji, Y.; Hu, S.; Liu, J.; Wei, L.; Luo, C.; Ukleev, V.; Radu, F.; Yan, W.; Chen, D.; Zhong, Z.; Gan, Y.; Chen, K.; Liao, Z.: High-temperature ferromagnetic LaCo O3 triggered by interfacial electron transfer and exchange coupling. Physical Review B 109 (2024), p. 174423/1-7
10.1103/physrevb.109.174423
Abstract:
The perovskite oxide heterointerface is a complex and fascinating region where charge transfer dramatically alters the coupling between charge, spin, orbital, and lattice order, resulting in novel phenomena absent in bulk materials. Understanding and controlling these interfacial effects is crucial for designing and optimizing oxide heterostructures for potential applications. Specifically, charge transfer can stabilize and enhance the ferromagnetic order at the interface, effectively improving the properties of magnetic materials. In this work, a detailed investigation of the LaCoO3/La2/3Sr1/3MnO3 heterostructures revealed Mn-Co ferromagnetic coupling induced by charge transfer at the interface. Remarkably, this interfacial ferromagnetic coupling dramatically increased the Curie temperature of the LaCoO3 film up to 190 K, which is significantly higher than the single LaCoO3 film. Using surface-sensitive x-ray absorption spectra and x-ray magnetic circular dichroism, we find sizable Co2+ forms from the charge transfer between Mn-Co sites at the interface. Combined with density functional theory calculations, it is clear that the 𝑒𝑔0−O−𝑒𝑔2 type Mn4+−O−Co2+ superexchange interaction is at the root of the strong ferromagnetic coupling behavior. This work demonstrates that interface modulation in perovskite heterostructures can be a powerful tool for manipulating overall magnetism. It also underscores that perovskite oxide interfaces provide an ideal platform for exploring intricate interactions between different order parameters and inducing novel interfacial effects.