Study of Electronic States in LaNiO3/SrRuO3 Bilayers: Interface-Induced Magnetism and Charge Transfer

The results of a study on the electronic states and valence band offset (VBO) in heterostructures of the transition metal oxide LaNiO3 (LNO)/SrRuO3 (SRO) grown on (001) SrTiO3 (STO) substrates are reported. X-ray photoelectron spectroscopy (XPS) data reveal the presence of Ni2+ states in LNO layer that can develop a reduced bandwidth of O-2p and Ni-3d. Further analysis of XPS data confirms the presence of a VBO, and the value of VBO is found to be +0.02 eV and -0.38 eV for the bilayers of STO/LaNiO3/SrRuO3 (BL-1) and STO/SrRuO3/LaNiO3 (BL-2), respectively. Distinct signs of VBO are noticed between the bilayers due to the relative shift of the valence band of the top layer with respect to the bottom layer. Such band shifts can lead to the charge transfer across the (3d-4d) interface, which significantly modifies the global electronic transport and magnetic properties of the bilayers. A detailed discussion on the underlying physical phenomena of electrical transport and magnetic responses triggered by the interface is also incorporated herein.