Ferroelectricity and Ferromagnetism Achieved via Adjusting Dimensionality in BiFeO₃/BiMnO₃ Superlattices

Integrating characteristics of materials through constructing artificial superlattices (SLs) has raised extensive attention in multifunctional materials. Here, we report the synthesis of BiFeO3/BiMnO3 SLs with considerable ferroelectric polarizations and tunable magnetic moments. The polarization of BiFeO3/BiMnO3 SLs presents a decent value of 12 μC/cm2, even as the dimensionality of BiFeO3 layers per period is reduced to about five-unit cells when keeping the BiMnO3 layers same. Moreover, it is found that the tunable magnetic moments of SLs are linked intimately to the dimensionality of BiFeO3 layers. Our simulations demonstrate that the superexchange interaction of Fe–O–Mn tends to be antiferromagnetic (AFM) with a lower magnetic domain formation energy rather than ferromagnetic (FM). Therefore, as the dimensionality of BiFeO3 per period is reduced, the AFM superexchange interaction between BiFeO3 and BiMnO3 in the SLs becomes weak, promoting a robust magnetization. This interlayer modulation effect in SLs presents an alluring way to accurately control the multiple order parameters in a multiferroic oxide system.