Electrical characterization of PMN–28 PT(001) crystals used as thin-film substrates

Ferroelectric and piezoelectric properties of (001) 0.72PbMg_1/3Nb_2/3O₃–0.28PbTiO₃ (PMN–28%PT) single crystals have been investigated from cryogenic temperatures to 475 K. PMN–28%PT is used as piezoelectric substrate, e.g., in multiferroic heterostructures. Electric field-induced phase transformations have been examined by electrical characterization including measurements of polarization loops, dielectric permitivitty, and the resistance change in La_0.7Sr_0.3MnO₃ films deposited on the (001) face. The relaxor ferroelectric transition behavior was studied by means of time-dependent current measurements. A phase diagram is set up. PMN–28%PT is found to be at the border of the appearance of the monoclinc phase (M_C) bridging the rhombohedral-tetragonal (R-T) transformation at higher PbTiO₃ contents. Measurements of the lattice expansion reveal that a high piezoelectric effect persists down to low temperatures. Therefore, PMN–28%PT single crystals are found to be appropriate substrates for application of piezoelectric strain to thin films over a broad temperature range.