Layer and spontaneous polarizations in perovskite oxides and their interplay in multiferroic bismuth ferrite

We review the concept of surface charge, first, in context polarization ferroelectric materials and, second, layers charged ions ionic insulators. While former is traditionally discussed ferroelectrics community and latter science community, we remind reader that two descriptions are conveniently unified within modern theory polarization. In both cases, charge leads to electrostatic instability—the so-called “polar catastrophe”—if it not compensated, range phenomena arise as a result different compensation mechanisms. illustrate these concepts using example prototypical multiferroic bismuth ferrite, BiFeO3, which unusual its spontaneous arising from layer charges can be same magnitude. As result, for certain combinations orientation termination, self-compensating. use density functional calculations BiFeO3 slabs superlattices, analysis high-resolution transmission electron micrographs, examples literature explore consequences this peculiarity.