Relationship between charge redistribution and ferromagnetism at the heterointerface between the perovskite oxides LaNiO3 and LaMnO3

To investigate the relationship between the charge redistribution and ferromagnetism at the interface between perovskite transition-metal oxides LaNiO3 (LNO) and LaMnO3 (LMO), we performed x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) measurements on the sandwiched layer in the trilayer structures. In the LNO/LMO heterostructures, one electron (hole) per unit-cell area is transferred from Mn (Ni) to Ni (Mn) ions across the interface unless there is a spatial limitation in the layer accommodating the transferred charges. A detailed analysis of the Ni-L-2,L-3 and Mn-L-2,L-3 XMCD spectra reveals that the magnetization of Ni ions is induced only in Ni2+ ions at the interface, while that of Mn ions is induced in both Mn3+ and Mn4+ ions. Combining these results with the previous XAS results on bilayer structures revealing the asymmetric charge redistribution of the LNO/LMO interface [Kitamura et al., Appl. Phys. Lett. 108, 111603 (2016)] shows that Ni magnetization is induced only in the Ni2+ ions of the 1 ML LNO adjacent to the interface, while the magnetization of Mn ions is increased in the 3-4 ML LMO of the interfacial region. These results indicate a close relationship between the charge redistribution due to the interfacial charge transfer and the ferromagnetism of the LNO/LMO interface. Furthermore, the XMCD spectra clearly demonstrate that the vectors of induced magnetization of both ions are aligned ferromagnetically, suggesting that the delicate balance between the exchange interactions occurring inside each layer and across the interface may induce the canted antiferromagnetism of Ni2+ ions, resulting in weak magnetization in the 1 ML LNO adjacent to the interface.