Steplike Switching in Symmetric $\mathrm{Pb}{\mathrm{Zr}}_{0.2}{\mathrm{Ti}}_{0.8}{\mathrm{O}}_{3}/{\mathrm{CoFe}\mathrm{O}}_{4}/\mathrm{Pb}{\mathrm{Zr}}_{0.2}{\mathrm{Ti}}_{0.8}{\mathrm{O}}_{3}$ Heterostructures for Multistate Ferroelectric Memory

Steplike Switching in Symmetric $Pb {Zr}_{0.2} {Ti}_{0.8} O_{3} / {CoFe O}_{4} / Pb {Zr}_{0.2} {Ti}_{0.8} O_{3}$ Heterostructures for Multistate Ferroelectric Memory

Andra Georgia Boni, Cristina Chirila, Iuliana Pasuk, Raluca Negrea, Ioana Pintilie, and Lucian Pintilie

Phys. Rev. Applied 8, 034035 – Published 28 September 2017

Abstract

A hysteresis loop with three polarization states is obtained in the case of a symmetric epitaxial ferroelectric-interlayer-ferroelectric structure with bottom and top ${SrRuO}_{3}$ electrodes. The ferroelectric layers are of $Pb {Zr}_{0.2} {Ti}_{0.8} O_{3}$ , while the interlayer is ${CoFe}_{2} O_{4}$ . It is shown that the three polarization states can be separately accessed, suggesting that this type of structure can be used as building element for a three-state nonvolatile ferroelectric random-access memory (FERAM). The presence of the three-state memory effect is explained through a simple phenomenological model based on Landau-Ginzburg-Devonshire theory. The findings of this study can pave the way to multistate all-oxide FERAM devices, resulting in a 50% increase in the storage density compared to actual nonvolatile memories.