Resistive Switching and Redox Process at the BaTiO 3 /(La,Sr)MnO 3 Multiferroic‐Type Interface
Résumé
Resistive switching in oxide‐based structures is intensively studied for the development of ultra‐fast non‐volatile memories with low consumption and neuromorphic electronic devices. Here, evidence of interface‐controlled, reversible, bi‐polar resistance switch in prototype multiferroic BaTiO3/La0.75Sr0.25MnO3 (BTO/LSMO) system is given. The analysis of current–voltage hysteresis curves of a thick Au/BTO/LSMO structure reveals the existence of a 2.55 nm‐thick barrier layer at the bottom BTO/LSMO interface, leading to a tunnel electroresistance of ≈1700%. In the native state where BTO polarization points downward, high resolution electron microscopy and electron energy loss spectroscopy show Ba/(La,Sr) and Ti/Mn cationic intermixing, together with a valency reduction of Mn cations and an oxygen deficiency at the interface. This results in a high resistance state, due to partial loss of the metallicity and of the double exchange magnetic interaction in the oxygen‐deficient LSMO. The switch to the low resistance state, achieved by upward electric field, is explained in terms of re‐oxydation of Mn cations at the interface (decrease of the Mn3+/Mn4+ ratio), with oxygen vacancies migration from LSMO to BTO. This work emphasizes the crucial role of ionic exchanges and of redox processes at interfaces, both on ferroelectric bound charge screening and on resistive switching.