Interfacial effect and strain on the electrical and magnetic properties of SrRuO/NdNiO bilayers with 3D island surface layer

3d–4d perovskite oxide SrRuO/NdNiO (SRO/NNO) bilayers were epitaxially deposited on (001)- and (011)- LaAlO (LAO) substrates by polymer-assisted deposition (PAD), respectively, and the electrical and magnetic properties have been investigated. It is found that the epitaxial growth tends to be 2D step flow or layer by layer for NdNiO films, but 3D island mode for SrRuO films, under PAD. The growth in 3D island mode is beneficial to the lattice relaxation. An abnormal behavior, i.e., the transport properties are mainly dominated by NNO layer, rather than the top SRO layer, is found in SRO/NNO bilayers. The interfacial effects, including the interlayer exchange coupling and the interfacial Ni (3d)-O (2p)-Ru (4d) orbital hybridization/reconstruction, are confirmed in SRO/NNO bilayers. Meanwhile, it is found that the strain-induced structural adjustment of the sole NNO layer directly affects the interfacial structure, including Ni–O bond and Ni–O-Ru bond angle, and the magnetic pinning function on the SRO layer. It is suggested that due to the special island-shape SRO layer, the competition and combination of the strain effect on the NNO layer and the interfacial effect in SRO/NNO bilayers dominate the interfacial properties with substrate-orientation dependence. The physical properties of the bilayers can be controlled by the sole single-layer structure through the substrate-induced strain and interface engineering, respectively.