Fig. 3.

PFM and discovery of novel phenomena. a Tunneling electroresistance effect verified by spatially resolved correlation between the onset of polarization reversal revealed by PFM and a resistive switching imaged by C-AFM. A change in PFM contrast correlates with the transition from low current (dark contrast) to high current (bright contrast). (Adapted with permission from ref. ²⁹. Copyright 2009 American Chemical Society). b Magnetic field control of ferroelectric domains in the multiferroic solid solution of lead zirconium titanate and lead iron tantalite (PZTFT): PFM images reveal a change in the ferroelectric domain structure, which depends on the orientation of the external magnetic field. (Adapted by permission from Springer Nature: ref. ⁶²). c Emerging topologic domain structures: flux-closure domain formation in a microscale single-crystalline BaTiO₃ lamella revealed by vector PFM. The image size is 2 × 2 µm². (Reprinted by permission from Springer Nature: ref. ⁶⁶). d Domain wall conductivity: the 6 × 6 µm² lateral PFM image obtained on a ErMnO₃ crystal with arrows indicating the in-plane polarization direction. The inset shows a C-AFM image acquired at the same location revealing different conductance for different types of domain walls. (Reprinted by permission from ref. ⁶⁹). e Flexoelectric control of polarization: in ultrathin ferroelectric films, a strain gradient, generated by PFM tip pressure, can produce a flexoelectric field high enough to exceed the coercive field of the film resulting in purely mechanical switching of nanoscale domains. f Enhancement of photovoltaic current (C-AFM image in the upper panel) at domain walls (PFM phase image in the lower panel). The size of each panel is 3.0 × 1.5 µm². (Adapted from ref. ⁸⁶ under the terms of the CC-BY 4.0 license)