Designing new ferroelectrics with a general strategy

Abstract

Abstract The presence of a switchable spontaneous electric polarization makes ferroelectrics ideal candidates for the use in many applications such as memory and sensors devices. Since known ferroelectrics are rather limited, finding new ferroelectric materials has become a flourishing field. One promising route is to design the improper ferroelectrics. However, previous approach based on the Landau theory is not easily adopted for systems that are unrelated to the Pbnm perovskite structure. To this end, we develop a general design rule that is applicable to any system. By combining this rule with the density functional theory calculations, we identify previously unrecognized classes of ferroelectric materials. It is shown that the $$R\bar{3}c$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>R</mml:mi><mml:mover><mml:mrow><mml:mn>3</mml:mn></mml:mrow><mml:mo>̄</mml:mo></mml:mover><mml:mi>c</mml:mi></mml:math> perovskite structure can become ferroelectric by substituting half of the B-site cations. Compound ZnSrO 2 with a non-perovskite layered structure can also be ferroelectric through the anion substitution. Moreover, our approach can be used to design new multiferroics as illustrated in the case of fluorine substituted LaMnO 3 .