High‐<i>T</i>_C Interfacial Ferromagnetism in SrMnO₃/LaMnO₃ Superlattices

Abstract

Abstract Heterostructures of strongly correlated oxides demonstrate various intriguing and potentially useful interfacial phenomena. LaMnO 3 /SrMnO 3 superlattices are presented showcasing a new high‐temperature ferromagnetic phase with Curie temperature, T C ≈360 K, caused by electron transfer from the surface of the LaMnO 3 donor layer into the neighboring SrMnO 3 acceptor layer. As a result, the SrMnO 3 (top)/LaMnO 3 (bottom) interface shows an enhancement of the magnetization as depth‐profiled by polarized neutron reflectometry. The length scale of charge transfer, λ TF ≈2 unit cells, is obtained from in situ growth monitoring by optical ellipsometry, supported by optical simulations, and further confirmed by high resolution electron microscopy and spectroscopy. A model of the inhomogeneous distribution of electron density in LaMnO 3 /SrMnO 3 layers along the growth direction is concluded to account for a complex interplay between ferromagnetic and antiferromagnetic layers in superlattices.