Magnetic modulations in (La,Sr)MnO3 heterostructures via interfacial oxygen vacancy engineering

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The control of interfacial oxygen vacancy provides additional functional tunability to correlated oxide heterostructures. Here, we studied the role of amorphous capping layers, such as LaAlO3 and LaMnO3, in controlling magnetic properties of (La,Sr)MnO3//SrTiO3 heterostructures. When (La,Sr)MnO3 layers are thin (∼4 nm), the amorphous LaAlO3 capping layer significantly suppresses the ferromagnetic interaction, denoted by a decreased Curie temperature TC (ΔTC over −300 K) and saturated moment MS (ΔMS at −2.9 μB/Mn) compared to the uncapped counterparts, irrespective of epitaxial orientations. This ferromagnetic suppression is attributed to the creation of interfacial oxygen vacancies, as evidenced by the recovery of ferromagnetism upon ex situ annealing (1 h at 625 °C in air). Moreover, when replacing LaAlO3 with LaMnO3, the reduction of oxygen affinity in the capping layer results in less pronounced magnetic modulations with ΔTC at −100 K and ΔMS at −1.1 μB/Mn. Also, the increase in (La,Sr)MnO3 layer thickness dilutes the capping-layer effect, leading to negligible changes on TC and MS in the LaAlO3-capped 40-nm-thick (La,Sr)MnO3//SrTiO3 samples. Our results not only shed some light on understanding the capping-layer effect in manganite-based heterostructures but also offer a feasible strategy for functional modulations at other oxide interfaces.