Magnetoelectric effects in SrRuO$_{3}$/BaTiO$_{3}$ heterostructures: A First Principles Study

Ferroelectric materials in combination with ferromagnets have emerged as structures in which strong magnetoelectric coupling may exist originating from unconventional physical mechanisms. The use of oxides such as SrRuO$_{3}$ as a metal electrode has been found to be of fundamental importance for the realization of ferroelectric films with critical thicknesses down to three unit cells. Here we present a study of SrRuO$_{3}$/BaTiO$_{3}$ heterostructures within the framework of density functional theory. This heterostructure is interesting since SrRuO$_{3}$ is a weak ferromagnetic oxide metal and hence, when used as an electrode on BaTiO$_{3}$, presents the possibility of coupling between electric and magnetic order parameters. In particular we study the magnetoelectric (ME) effect at the interface of SrRuO$_{3}$/BaTiO$_{3}$ by treating SrRuO$_{3}$ as spin polarized metal. We find that magnetic properties at the interface are affected as the ferroelectric polarization in the BaTiO$_{3}$ is reversed. We discuss the origins of ME effect and compare them with previously proposed ME coupling mechanisms in Fe/BaTiO$_{3}$, Fe$_{3}$O$_{4}$/BaTiO$_{3, }$and SrRuO$_{3}$/SrTiO$_{3}$ heterostructures$^{1, 2}$. $^{1}$Niranjan et al., Phys. Rev. B, \textbf{78}, 140405 (2008); $^{2}$Rondinelli et al., Nat. Nanotechnology, \textbf{3,} 46, (2008)