Charge Transfer Control of Emergent Magnetism at SrMnO₃/LaMnO₃ Interfaces

Abstract Emergent phases at the interfaces in strongly correlated oxide heterostructures display novel properties not akin to those of constituting materials. The interfacial ferromagnetism in (LaMnO₃)_m/(SrMnO₃)_n (LMO)_m/(SMO)_n superlattices (SLs) with antiferromagnetic bulk LMO and SMO layers is believed to be a result of the interfacial charge transfer (CT). By using in situ optical ellipsometry, it is demonstrated directly that CT and emergent magnetism in (LMO)_m/(SMO)_n SLs are controlled by the LMO/SMO thickness ratio, chosen as m/n = 1 and 2. The enhanced CT in SLs with m/n = 2 favors the high‐T_C emergent ferromagnetism with T_C = 350–360 K, whereas the reduced CT in m/n = 1 SLs suppresses it yielding T_C = 300 K. A complex dependence of the saturation magnetization as a function of interface density Λ = (m + n)⁻¹ with minima at Λ = 0.11 (m/n = 2) and Λ = 0.25 (m/n = 1) was observed and rationalized by the competition of ferromagnetic and antiferromagnetic contributions, originating from the volume of LMO and SMO layers as well as from the LMO/SMO interfaces. The role of epitaxy stress and MnO₆ octahedral tilts in the emergent magnetic behavior is discussed.