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.
@article{arxiv.1602.03678,
title = {Exchange coupling inversion in a high-spin organic triradical molecule},
author = {R. Gaudenzi and E. Burzurí and D. Reta and I. de P. R. Moreira and S. T. Bromley and C. Rovira and J . Veciana and H. S. J. van der Zant},
journal= {arXiv preprint arXiv:1602.03678},
year = {2016}
}