Interplay of bulk and interface effects in the electric-field driven transition in magnetite

TL;DR

This study investigates the electric-field-driven phase transition in magnetite thin films, revealing the roles of contact and bulk effects, and supports the charge gap closure mechanism through experimental evidence.

Contribution

It provides a detailed experimental analysis of contact and bulk effects in the electric-field-induced transition in magnetite, supporting the charge gap closure theory.

Findings

Contact resistances decrease abruptly at transition onset

Magnetite channel resistance drops sharply during transition

Transport is thermally activated below the Verwey temperature

Abstract

Contact effects in devices incorporating strongly-correlated electronic materials are comparatively unexplored. We have investigated the electrically-driven phase transition in magnetite (100) thin films by four-terminal methods. In the lateral configuration, the channel length is less than 2 $\mu$m, and voltage-probe wires $\sim$100 nm in width are directly patterned within the channel. Multilead measurements quantitatively separate the contributions of each electrode interface and the magnetite channel. We demonstrate that on the onset of the transition contact resistances at both source and drain electrodes and the resistance of magnetite channel decrease abruptly. Temperature dependent electrical measurements below the Verwey temperature indicate thermally activated transport over the charge gap. The behavior of the magnetite system at a transition point is consistent with a theoretically predicted transition mechanism of charge gap closure by electric field.