Designing a mechanically driven spin-crossover molecular switch via organic embedding

TL;DR

This paper proposes a mechanically controlled spin-crossover device using Fe-porphyrin embedded in organic graphene nanoribbons, demonstrating a strain-induced magnetic state change and a significant current toggle for molecular spintronics.

Contribution

It introduces a novel mechanically driven spin-switch design utilizing organic embedding and advanced computational methods to predict strain-induced magnetic and electronic switching.

Findings

Strain triggers a low-spin to high-spin crossover in FeP.

Current through the device changes by over an order of magnitude.

Organic embedding with graphene electrodes enhances reliability.

Abstract

Among spin-crossover complexes, Fe-porphyrin (FeP) stands out for molecular spintronic applications: An intricate, yet favourable balance between ligand fields, charge transfer, and the Coulomb interaction makes FeP highly manipulable, while its planar structure facilitates device integration. Here, we theoretically design a mechanical spin-switch device in which external strain triggers the intrinsic magneto-structural coupling of FeP through a purely organic embedding. Exploiting the chemical compatibility and stretchability of graphene nanoribbon electrodes, we overcome common reliability and reproducibility issues of conventional inorganic setups. The competition between the Coulomb interaction and distortion-induced changes in ligand fields requires methodologies beyond the state-of-the-art: Combining density functional theory with many-body techniques, we demonstrate experimentally feasible tensile strain to trigger a low-spin ($S=1$) to high-spin ($S=2$) crossover. Concomitantly, the current through the device toggles by over an order of magnitude, adding a fully planar mechanical current-switch unit to the panoply of molecular spintronics.