Journal
NATURE
Volume 449, Issue 7164, Pages 881-U7Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/nature06165
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The motion of domain walls is critical to many applications involving ferroelectric materials, such as fast high-density non-volatile random access memory(1). In memories of this sort, storing a data bit means increasing the size of one polar region at the expense of another, and hence the movement of a domain wall separating these regions. Experimental measurements of domain growth rates in the well-established ferroelectrics PbTiO(3) and BaTiO(3) have been performed, but the development of new materials has been hampered by a lack of microscopic understanding of how domain walls move(2-11). Despite some success in interpreting domain-wall motion in terms of classical nucleation and growth models(12-16), these models were formulated without insight from first-principles-based calculations, and they portray a picture of a large, triangular nucleus that leads to unrealistically large depolarization and nucleation energies(5). Here we use atomistic molecular dynamics and coarse-grained Monte Carlo simulations to analyse these processes, and demonstrate that the prevailing models are incorrect. Our multi-scale simulations reproduce experimental domain growth rates in PbTiO(3) and reveal small, square critical nuclei with a diffuse interface. A simple analytic model is also proposed, relating bulk polarization and gradient energies to wall nucleation and growth, and thus rationalizing all experimental rate measurements in PbTiO(3) and BaTiO(3).
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