Realization of a strong ferroelectric metal by Nb-doping in strained EuTiO3

Abstract Ferroelectric (FE) metals have been attracting attention as they possess both metallicity and ferroelectricity, the two seemingly incompatible physical properties. An important problem for both fundamental research and potential applications is how to realize a strong FE metal. One strategy is to dope a strong FE insulator and turn it into an FE metal, provided that the induced free electrons do not destroy FE distortion. Strained EuTiO 3 is a strong FE ferromagnet and a promising candidate for such a strategy. Here, we calculate the structural, electronic, and polarization properties of Nb-doped strained EuTiO 3 using the hybrid density-functional theory. The results show that the strained EuTi 0.875 Nb 0.125 O 3 is a strong FE metal as the Nb doping induces metallicity without weakening the FE distortion. The underlying atomistic mechanism of the coexistence of metallicity and strong ferroelectricity is discussed. The findings show that combining doping and strain engineering is a promising way to realize new EuTiO 3 -based strong FE metals and may be used in other materials as well.