Multiscale Domain Structures and Ferroic Properties of Dy-Modified BiFeO₃-PbTiO₃ Single Crystals

Single-phase multiferroic BiFeO3-based perovskite solid solutions attract great research interest due to the coexistence of ferroelectric and magnetic orderings above room temperature. In this work, the single crystals of the 0.5(Bi0.9Dy0.1)FeO3-0.5PbTiO3 ternary system are successfully grown and their structure and ferroic properties are characterized by a variety of techniques. X-ray diffraction reveals the tetragonal crystal structure. The ferroelectric Curie temperature is found to be ≈670 K from the dielectric and thermal measurements. The domain structures on multiple scales are investigated by polarized light and atomic force and piezoresponse force microscopies on the 001 orientated single crystals. Hierarchical domain configurations are revealed and explained based on the mechanical/electrical compatibility principles. The a-a- and a-c-type 90° domains are widely distributed with size from sub-micrometer to dozens of micrometers. The domain evolutions after poling with various applied electric fields have also been investigated. Saturated ferroelectric hysteresis loops are obtained at room temperature with a remanent polarization of 9.0 μC/cm2. The Mössbauer spectroscopy investigations demonstrate the multiple local states of magnetic Fe3+ ions. The room-temperature paramagnetic nature develops into an antiferromagnetic order at TN = 55 K. The findings of multiferroic domain walls give rise to the Dy-BFPT single-crystal potential for the domain wall nanoelectronics.