AFM-tip written normal and anomalous domains in PMN-0.4PT crystals

摘要

At present, crystals of the solid solutions Pb(Mg1/3Nb2/3)O-3-xPbTiO(3) (PMN-xPT) are under intensive investigation due to their excellent piezoelectric characteristics. Studies in domain engineering are of importance for an insight into the contribution from the domain formation and resulting domain-wall density to piezoelectric coefficients. In this work, the fabrication of domains by dc AFM-tip voltages was studied in the tetragonal PMN-0.4PT crystals. Two types of domains were observed, either uniformly polarized along the poling field (the "normal" ones), or, following the commonly accepted term, "anomalous" ones containing a small area with the polarization directed oppositely to the poling field. In this work, for the first time, the correlation between the domain shape and the local piezoelectric hysteresis loops H-omega-U-tip was found, namely, the larger is the local bias voltage U-b, the higher is the tip voltage U-tip at which the anomalous domains appear. This finding relates the observed scatter in the exposure conditions corresponding to the anomalous domains formation, to the non-uniform spatial distribution of the local bias fields. The domain diameter D vs U-tip and pulse duration t(p) were investigated for U-tip <= 50 V and t(p) from 10 ms to 10 s. The exposure characteristics are independent of the domain shape. For a given t(p), D(U-tip) is described by a unified linear function in the whole U-tip range. The curves D(t(p)) follow a power law D similar to t(p)(k) with the exponent k varying very weakly with U-tip. The relaxation kinetics of anomalous domains depends on the writing conditions. The normal domains are found to decay significantly faster than the anomalous ones, with the decay kinetics depending on the domain spacing.