New design strategy for realizing multiferroic materials

Ferroelectricity is a property that only insulating materials can exhibit. % For this reason, nearly all searches for new multiferroic compounds, those simultaneously exhibiting ferroelectric and magnetic order, have focused on \emph{insulating} magnetic oxides. % Here, we propose a different approach: Start from a \emph{conducting} oxide with broken inversion symmetry and search for routes to induce long-range magnetic order [1]. % Using density-functional and dynamical mean-field theories, we investigate the electronic properties of the polar metallic oxide LiOsO$_3$. % We show that a multiferroic state can be engineered by enclosing LiOsO$_3$ between an insulating material, LiNbO$_3$. % We predict that the 1/1 superlattice of LiOsO$_3$ and LiNbO$_3$ exhibits strong coupling between magnetic and ferroelectric degrees of freedom with a ferroelectric polarization of 41.2 $\mu$Ccm$^{-2}$, Curie temperature of 927\,K, and N\'eel temperature of 379\,K. % Our results show that one can start with polar metallic oxides to make multiferroics.\\[1em] [1] D.\ Puggioni \emph{et al}, Phys.\ Rev.\ Lett.\ \textbf{115}, 087202 (2015).