Effects of Interactions and Defect Motion on Ramp Reversal Memory in Locally Phase Separated Materials

TL;DR

This paper extends a defect motion model to include domain interactions in phase-separated TMOs, accurately predicting ramp reversal memory effects and offering insights for optimizing neuromorphic device performance.

Contribution

It introduces a combined model of the Random Field Ising Model with defect diffusion to better explain RRM and its dependence on domain interactions in TMOs.

Findings

Maximum RRM occurs near the inflection point of the warming branch.

Increasing nearest-neighbor interactions enhances the RRM effect.

Model predictions align with experimental observations on VO$_2$.

Abstract

The ramp-reversal memory (RRM) effect in metal-insulator transition metal oxides (TMOs), a non-volatile resistance change induced by repeated temperature cycling, has attracted considerable interest in neuromorphic computing and non-volatile memory devices. Our previously introduced defect motion model successfully explained RRM in vanadium dioxide (VO$_2$), capturing observed critical temperature shifts and memory accumulation throughout the sample. However, this approach lacked interactions between metallic and insulating domains, whereas the RRM only appears when TMOs are brought into the metal-insulator coexistence regime. Here, we extend our model by combining the Random Field Ising Model with defect diffusion-segregation, thereby enabling accurate hysteresis modeling while predicting the relationship between RRM and domain interactions. Our simulations demonstrate that maximum RRM occurs when the turnaround temperature approaches the warming branch inflection point, consistent with experimental observations on VO$_2$. Most significantly, we find that increasing nearest-neighbor interactions enhances the maximum memory effect, thus providing a clear mechanism for optimizing RRM performance. Since our model employs minimal assumptions, we predict that RRM should be a widespread phenomenon in materials exhibiting patterned phase coexistence of electronic domains. This work not only advances fundamental understanding of memory behavior in TMOs but also establishes a much-needed theoretical framework for optimizing device applications.