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

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Spin-crossover (SCO) complexes, particularly iron-porphyrin (FeP), are promising for molecular spintronics due to their tunable spin states.
• FeP's planar structure and balanced electronic interactions offer potential for device integration, but reliable mechanical control remains a challenge.

Purpose of the Study:

• To theoretically design a novel mechanical spin-switch device utilizing FeP.
• To demonstrate the feasibility of using external tensile strain to control the spin state of FeP within a purely organic device architecture.

Main Methods:

• Combined density functional theory (DFT) with many-body techniques to model the spin-state transition.
• Employed graphene nanoribbon electrodes for mechanical strain application and current transport measurements.
• Investigated the interplay between Coulomb interaction and ligand field effects under strain.

Main Results:

• Demonstrated that experimentally feasible tensile strain can induce a spin-crossover from low-spin (S=1) to high-spin (S=2) in FeP.
• Observed a significant toggle in device current (over an order of magnitude) concomitant with the spin-state transition.
• Showcased a fully planar mechanical current-switch unit integrated with molecular spintronics.

Conclusions:

• The proposed FeP-based mechanical spin-switch offers a reliable and reproducible method for spin control in molecular spintronics.
• Graphene nanoribbons provide a compatible and stretchable platform for such organic spintronic devices.
• This work introduces a new paradigm for mechanical current switching at the molecular level.