Coexistence of ferroelectricity and metallicity in M-doped BaTiO3 (M = Al, V, Cr, Fe, Ni, and Nb): First-principles study

Ferroelectric materials are typically insulators, but recent studies have shown that ferroelectric materials can be modified by design for the coexistence of metallicity and ferroelectricity. Here, by using first-principles calculations, we investigated ferroelectric, electronic, and magnetic properties of different metal atoms M doped BaTiO3 (BTO) (M=Al, V, Cr, Fe, Ni, and Nb) system with a doping concentration of 0.125. Our results indicate that electrons in Cr-, Fe-, Ni-, and V-doped BTO systems are highly localized in the doping atom and its nearby O atoms. Simultaneously, their ferroelectricity has not decreased much. However, ferroelectricity and metallicity can perfectly coexist in each unit cell of an Al-doped BTO system owing to its p-type conductivity that is nonmagnetic, which is predominantly contributed by px/py orbitals. Moreover, the ferroelectricity of an Al-doped BTO system is uncommonly enhanced. Besides, for a Nb-doped BTO system, the ferromagnetic n-type conductivity exists in each unit cell, and its ferroelectricity is reduced because of the existence of dxz/dyz orbital electrons that eliminate the out-of-plane electrical dipoles. Our results provide a new avenue to tune ferroelectric and ferromagnetic properties in multiferroic perovskites.