EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Molecular spintronics involving spin-state switching in first-row transition-metal organic complexes has seen rapid progress in recent decades. In particular, molecular complexes hosting Fe, Co, Ni, or Mn ions can exhibit multiple spin-states depending on a subtle balance between molecular ligand field and Coulomb interaction. However, integration of such molecules into a spin-switch device remains a major challenge, mainly due to the poor reliability and reproducibility of how the molecule is contacted with metallic electrodes. Here, we propose a molecular-switch device with pure organic embedding, where iron-porphyrin bridges graphene nanoribbon electrodes that can potentially overcome these issues. Using density functional theory (DFT) and realistic many-body techniques combined with the Landauer-Büttiker formalism for transport properties, we explore the device under applied mechanical strain. We demonstrate a spin-crossover between low-spin (S=1) and high-spin (S=2) states, triggered at the experimentally feasible mechanical strain. We predict the change of the molecular spin state to toggle the current through the device by an order of magnitude.

We acknowledge financial support from the Science Foundation Ireland [19/EPSRC/3605] and the Engineering and Physical Sciences Research Council EP/S030263/1, European Research Council (Consolidator Grant No. 617196 CORRELMAT), SFI-EPSRC, Austrian Science Fund (FWF) through project ’LinReTraCe’ P 30213-N36 (JMT, AV) and project P 31631 (AV).