Nanoscale investigation of polar structure of (1-x)PbMg _1/3Nb_2/3O₃-xPbTiO₃ single crystals

(1-x)PbMg_1/3Nb_2/3O₃-xPbTiO₃ (PMN-PT) single crystals of different compositions were studied via piezoresponse force microscopy (PFM). Piezoelectric contrast has been observed in 0.9PMN-0.1PT above the temperature of structural transition indicating spatial distribution of polarization and was attributed to the existence of polar clusters. The domain patterns were found to change drastically with increasing Ti content. In particular, the piezoresponse images of 0.8PMN-0.2PT combine both relaxor and ferroelectric features and in 0.65PMN-0.35PT crystals only micron-sized ferroelectric domains were observed. The evolution of the polar structures with increasing temperature and under external electric field was also investigated. The nature of the observed phenomena is discussed based on the current understanding of the relaxor state in ferroelectrics and possible influence of PFM instrumentation.