2.

Reversibility of atmosphere-driven changes in domain wall conductance. cAFM scans taken (a) after annealing in N₂ at 300 °C for 48 h, (b) after subsequent heating up to 200 °C in N₂ and synthetic air, (c) after repeated annealing in N₂ at 300 °C for 48 h, and (d) after repeated heating up to 200 °C in N₂ and synthetic air (see Supporting Information for details). After annealing, the samples were exposed to ambient conditions for ≤ 30 min before the cAFM scans started. (e) Current profiles extracted along the white markings in (a–d). The profiles are normalized such that the +P (−P) domains have an average current value of 0 (1). (f) Relative domain wall conductance ΔI for the four profiles in panel (e). By exposing the system to different atmospheres, ΔI switches between conductive (ΔI ≫ 0) and insulating (ΔI < 0) behavior. The cAFM scans are performed with diamond-coated tips DEP01 for panels (a–c) and CDT-NCHR for panel (d) and bias voltages of (a) 2 V, (b) 4 V, (c) 5 V, and (d) 5 V. All cAFM scans are performed at room temperature in air. Data taken in different regions of the sample show qualitatively equivalent results regarding the annealing-driven changes in conductance (Figure S2), confirming the effect across the entire sample surface.