Stress-Induced Transformations of Polarization Switching in CuInP2S6 Nanoparticles

Using the Landau-Ginzburg-Devonshire approach, we study stress-induced transformations of polar-ization switching in ferrielectric CuInP2S6 nanoparticles for three different shapes: a disk, a sphere, and a needle. Semiconducting properties of a nanoparticle are modeled by a surface-charge layer, whose effec-tive screening length can be rather small due to the field effect. We reveal a very strong and unusual influence of hydrostatic pressure on the appearance of polarization switching in CuInP2S6 nanoparticles, hysteresis loop shape, magnitude of the remanent polarization, and coercive fields, and explain the effects by the anomalous temperature dependence and "inverted" signs of CuInP2S6 linear and nonlinear elec-trostriction coupling coefficients. In particular, by varying the sign of the applied pressure (from tension to compression) and its magnitude (from zero to several hundreds of MPa), quasistatic hysteresisless paraelectric curves can transform into double, triple, pinched, or single hysteresis loops. Unexpectedly, we predict that stressed CuInP2S6 nanospheres and nanoneedles reveal sizeable temperature and pressure ranges of triple loop stability, which are very rare in ferroelectrics and antiferroelectrics. A physical origin of triple loops is the coexistence of "small" and "larger" polarizations in the four-well ferrielectric state. Due to the sufficiently wide temperature and pressure ranges of double, triple, and pinched hysteresis loop stability (at least in comparison with many other ferroelectrics), CuInP2S6 nanodisks can be of par-ticular interest for applications in energy storage (in the region of double loops), CuInP2S6 nanospheres maybe suitable for dynamic random-access multibit memory, and CuInP2S6 nanoneedles are promising for nonvolatile multibit memory cells (in the regions of triple and pinched loops). The stress control of the polarization-switching scenario allows the creation of advanced piezosensors based on CuInP2S6 nanocomposites.