Large elastic nonlinearities can lead to elastic hysteresis behavior, which defines ferroelasticity in analogy to its sister ferroics: ferromagnetism and ferroelectricity. Ferroelasticity is the most common nonlinear effect in natural materials and plays a major role in the mineralogical behavior of the Earth's crust and mantle. It produces interfacial twin walls that act as sinks and sources for defects and that show localized effects such as superconducting twin boundaries and ferroelectricity, even when such effects do not exist in the bulk. The movement of twin walls under elastic forcing is creep-like, with some superimposed jerks due to pinning and unpinning by defects and jamming by other twin boundaries. This review applies Landau theory and discusses some aspects of the emerging field of domain boundary engineering.

The transport physics of domain wall conductivity in La-doped bismuth ferrite (BiFeO3) has been probed using variable temperature conducting atomic force microscopy and piezoresponse force microscopy in samples with arrays of domain walls in the as-grown state. Nanoscale current measurements are investigated as a function of bias and temperature and are shown to be consistent with distinct electronic properties at the domain walls leading to changes in the observed local conductivity. Our observation is well described within a band picture of the observed electronic conduction. Finally, we demonstrate an additional degree of control of the wall conductivity through chemical doping with oxygen vacancies, thus influencing the local conductive state.

It has long been stated that there are profound analogies between fracture experiments and earthquakes; however, few works attempt a complete characterization of the parallels between these so separate phenomena. We study the acoustic emission events produced during the compression of Vycor (${\mathrm{SiO}}_2$). The Gutenberg-Richter law, the modified Omori’s law, and the law of aftershock productivity hold for a minimum of 5 decades, are independent of the compression rate, and keep stationary for all the duration of the experiments. The waiting-time distribution fulfills a unified scaling law with a power-law exponent close to 2.45 for long times, which is explained in terms of the temporal variations of the activity rate.