First-principles investigation of morphotropic transitions and phase-change functional responses in BiFeO₃-BiCoO₃ multiferroic solid solutions

We present an ab initio study of the BFCO solid solution formed by multiferroics BiFeO₃ (BFO) and BiFeO₃ (BCO). We find that BFCO presents a strongly discontinuous morphotropic transition between BFO-like and BCO-like ferroelectric phases. Further, for all compositions such phases remain (meta)stable and retain well-differentiated properties. Our results thus suggest that an electric field can be used to switch between these structures and show that such a switching involves large phase-change effects of various types, including piezoelectric, electric, and magnetoelectric ones.