Colossal electroresistance mechanism in aAu∕Pr0.7Ca0.3MnO3∕Ptsandwich structure: Evidence for a Mott transition

Abstract

The resistive switching characteristics of $\mathrm{Au}∕{\mathrm{Pr}}_{0.7}{\mathrm{Ca}}_{0.3}\mathrm{Mn}{\mathrm{O}}_{3}(\mathrm{PCMO})∕\mathrm{Pt}$ sandwich structure were investigated by changing growth temperature of the PCMO film, adding an oxygen annealing process, and modifying the Au/PCMO/Pt sandwich structure by inserting a $\mathrm{Pr}\mathrm{Mn}{\mathrm{O}}_{3}$ (PMO) or $\mathrm{Ca}\mathrm{Mn}{\mathrm{O}}_{3}$ (CMO) layer at the Au/PCMO interface. From these experiments, we obtained the following results. First, only crystalline PCMO films exhibited reversible resistive switching behavior in Au/PCMO/Pt sandwich structure. Secondly, the ${\mathrm{Mn}}^{4+}∕{\mathrm{Mn}}^{3+}$ ratio at the PCMO surface was changed by oxygen annealing of the PCMO film, resulting in an increase of the resistance ratio of high resistance state and low resistance state. Lastly, we could not observe the resistive switching behavior in Au/PMO/PCMO/Pt and Au/CMO/PCMO/Pt sandwich structures. The resistive switching behavior could be observed only in Au/PCMO/PMO(or CMO)/PCMO/Pt sandwich structure. These results indicate that the resistive switching of Au/PCMO/Pt sandwich structure depends on the mixed valence state ${\mathrm{Mn}}^{4+}∕{\mathrm{Mn}}^{3+}$ of Mn ions in the metal/PCMO interface domains. This result can be regarded as evidence for a Mott transition.