Selective Pathways for 180° Polarization Switching in Rhombohedral BiFeO ₃ Heterostructures

Exploring tunable polarization switching in ferroelectric heterostructures is crucial for advancing information storage technologies and stabilizing nontrivial topological polar textures. Here, we study the evolution of polarization switching in (001)‐oriented rhombohedral BiFeO 3 layers, where 71°, 109°, and 180° switching variants coexist. As the BiFeO 3 layer thickness increases from 30 to 180 nm, the ratio of 180° polarization switching rises from 19.7% to 56.5%, accompanied by enhanced multidomain features. This trend contradicts the well‐known two‐step model for 180° switching, where the second step is driven by the ferroelastic relaxation that prefers lattice homogeneity. We attribute this to the opening of the unconventional single‐step 180° switching pathway. Unlike the two‐step pathway, the proposed single‐step collinear switching is expected to be less favored by a large out‐of‐plane electric field, due to the misalignment between the applied [001] field and the <111> polar axes. This is evidenced by the reduction of the 180° switching ratio (from 44.9% to 20.2%) with increasing voltage (from −3 to −15 V) in the 125‐nm‐thick layer. In contrast, the 40‐nm‐thick control sample shows an almost unchanged ratio (∼17%). Our findings provide new insights into understanding the dynamics of polarization switching in BiFeO 3 and expand the possibility for deterministic ferroelectric control.