Engineering Strong Magnetoelectricity Using a Hexagonal 2D Material on Electron-Doped Hexagonal LuFeO_3

Cubic perovskite-structure ABO_3 and A_1-xA^'_xBO_3-typeoxides have been investigated extensively while their hexagonal-structureversions have received minimal attention, even though they are multiferroic andcan form heterostructures with the manifold hexagonal two-dimensionalmaterials. Hexagonal ferrites of the form RFeO_3, where R is yttrium or arare-earth element such as Lu, Yb, etc., feature coupled ferroelectricity (FE)and weak-ferromagnetism (wFM), exhibiting linear magnetoelectricity. Their onlydrawback is weak ferromagnetism. In this paper, we employdensity-functional-theory (DFT) calculations on hexagonal LuFeO_3 (h-LFO),targeting its magnetic ordering by electron doping,anticipatingspin-disproportionation of the Fe sublattices. Indeed, we show thatspin-disproportionation in heavily-electron-doped versionsLu_1-xHf_xFeO_3 (h-LHFO), especially for x=1/3 and 1/2, leads torobust out-of-plane collinear ferrimagnetism that is stable at roomtemperature. Furthermore, the robust ferroelectricity of h-LFO persists via aJahn-Teller metal-to-insulator transition. Finally, we construct ah-LHFO/h-2D heterostructure, where h-2D stands for the FE/FM monolayerMnSTe, and demonstrate strong magnetoelectric coupling, namely manipulation ofmagnetic skyrmions in MnSTe by an external electric field through the h-LHFOpolarization, opening up a new realm for magnetoelectric applications.