Recently, antiferroelectric-like behavior has been unexpectedly observed in several studies on ${\mathrm{BiFeO}}_3$ (BFO) thin films and superlattices; however, this phenomenon has still received limited attention. In this work, we investigate $n/n {\mathrm{BiFeO}}_3/{\mathrm{SrRuO}}_3$ (BFO/SRO) multiferroic-metal superlattices based on density functional theory (DFT) calculations. Two complex polar ordering states were identified in the BFO/SRO superlattices, characterized by an in-plane polar order (IP phase) and an in-plane antipolar order (IAP phase). Meanwhile, both phases exhibit out-of-plane polar displacements, even in ultrashort-period superlattices. As the layer thickness increases up to $n=5$, the ground state transitions from the IP phase to the IAP phase. This process is analogous to a ferroelectric-to-antiferroelectric phase transition along the in-plane direction. The emergence of the antiferroelectric-like IAP phase is closely linked to the modulation of electrostatic boundary conditions. Furthermore, our analysis of the depolarization field with increasing layer thickness reveals a competition between the metallic screening effect and the depolarization field. This study provides insights for modulating the potential antiferroelectric-like phase in BFO-based electronic nanodevices.

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• Antiferroelectricity
• Ferroelectricity
• Antiferroelectrics
• Superlattices
• Density functional calculations
• First-principles calculations