Exchange coupling inversion in a high-spin organic triradical molecule

TL;DR

This study demonstrates that the magnetic exchange coupling in an organic triradical molecule can invert its sign due to structural distortions and can be electrically tuned, enabling controlled magnetic state reversal in molecular nanodevices.

Contribution

It reveals a sample-dependent exchange coupling inversion and electric tunability in an organic triradical molecule, advancing control over molecular magnetic states.

Findings

Sign inversion of exchange coupling due to structural distortions.

Electric gating enables in-situ tuning of magnetic interactions.

Transition from high-spin to low-spin ground state observed.

Abstract

The magnetic properties of a nanoscale system are inextricably linked to its local environment. In ad-atoms on surfaces and inorganic layered structures the exchange interactions result from the relative lattice positions, layer thicknesses and other environmental parameters. Here, we report on a sample-dependent sign inversion of the magnetic exchange coupling between the three unpaired spins of an organic triradical molecule embedded in a three-terminal device. This ferro-to-antiferromagnetic transition is due to structural distortions and results in a high-to-low spin ground state change in a molecule traditionally considered to be a robust high-spin quartet. Moreover, the flexibility of the molecule yields an in-situ electric tunability of the exchange coupling via the gate electrode. These findings open a route to the controlled reversal of the magnetic states in organic molecule-based nanodevices by mechanical means, electrical gating or chemical tailoring.