Stress-Induced Transformations of Polarization Switching in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:msub><mml:mrow><mml:mi>Cu</mml:mi><mml:mi>In</mml:mi><mml:mi mathvariant="normal">P</mml:mi></mml:mrow><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mrow><mml:mrow><mml:mi mathvariant="normal">S</mml:mi></mml:mrow></mml:mrow><mml:mn>6</mml:mn></mml:msub></mml:math> Nanoparticles

Abstract

Using the Landau-Ginzburg-Devonshire approach, we study stress-induced transformations of polarization switching in ferrielectric ${\mathrm{Cu}\mathrm{In}\mathrm{P}}_{2}{\mathrm{S}}_{6}$ 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 effective 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 ${\mathrm{Cu}\mathrm{In}\mathrm{P}}_{2}{\mathrm{S}}_{6}$ 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 ${\mathrm{Cu}\mathrm{In}\mathrm{P}}_{2}{\mathrm{S}}_{6}$ linear and nonlinear electrostriction 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 ${\mathrm{Cu}\mathrm{In}\mathrm{P}}_{2}{\mathrm{S}}_{6}$ 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), ${\mathrm{Cu}\mathrm{In}\mathrm{P}}_{2}{\mathrm{S}}_{6}$ nanodisks can be of particular interest for applications in energy storage (in the region of double loops), ${\mathrm{Cu}\mathrm{In}\mathrm{P}}_{2}{\mathrm{S}}_{6}$ nanospheres maybe suitable for dynamic random-access multibit memory, and ${\mathrm{Cu}\mathrm{In}\mathrm{P}}_{2}{\mathrm{S}}_{6}$ 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 ${\mathrm{Cu}\mathrm{In}\mathrm{P}}_{2}{\mathrm{S}}_{6}$ nanocomposites.

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