Tuning charge transfer and magnetic properties in LaCoO3/LaMnO3/LaCoO3 trilayers by oxygen content

In this manuscript, perovskite oxide LaCoO3/LaMnO3/LaCoO3 (LLL) trilayers and the single-layer LaMnO3 (LMO) and LaCoO3 (LCO) films are epitaxially grown on (001)-oriented SrTiO3 substrates by polymer-assisted deposition combining with heat treating in Ar, air, and O-2 atmospheres, respectively. The crystal structure and magnetic properties are investigated. It is found that the responses of LMO and LCO films to oxygen content are different, and the magnetic property of LMO is more sensitivity to oxygen content than that of LCO. The oxygen content can directly affect the structure and magnetic properties of LMO and LCO layers, which, in turn, modulate the interfacial magnetic properties of the LLL trilayers through interlayer coupling. By comparison with the magnetic properties of the single-layer films, an abnormal ferromagnetic (FM) transition is found in the LLL trilayers at around 216 K, besides two known FM transitions corresponding to those in the LCO and LMO layers, respectively. It is suggested that the abnormal FM transition is attributed to Mn4+-O-Co2+ FM super-exchange interaction, which is induced by the charge transfer from Mn3+ to Co3+ ions and the interlayer coupling between the LMO and LCO layers. The interlayer coupling of the trilayers, including the interfacial coupling and the diffusion-induced inlayer coupling, dominates the interface properties, which are tuned by oxygen content-dependent charge transfer. The cooperative function of the orbital/charge structure and the interlayer coupling dominates the magnetic properties of the LLL trilayer under the tensile strain. These findings provide new avenues to regulate the electronic and magnetic states of perovskite oxide multilayers and another way to the development of multifunctional electronic devices.