Field-induced percolation of polar nanoregions in relaxor ferroelectrics
S. Prosandeev, Dawei Wang, A. R. Akbarzadeh, B. Dkhil, and L. Bellaiche
Accepted
A first-principles-based effective Hamiltonian is used to investigate low-temperature properties of Ba(Zr,Ti)O3 relaxor ferroelectrics under an increasing dc electric field. This complex system progressively develops an electric polarization that is highly non-linear with the dc field. This development leads to a maximum of the static dielectric response at a critical field, Eth, and involves four different field regimes. Each of these regimes is associated with its own characteristic behavior of polar nanoregions (PNRs), such as shrinking, flipping and elongation of dipoles or change in morphology. Strikingly, clusters propagating inside the whole sample, with dipoles being parallel to the field direction, begin to form at precisely the Eth critical field. Such result, and further analysis we performed, therefore reveal that field-induced percolation of PNRs is the driving mechanism for the transition from the relaxor to ferroelectric state.