One of the primary objectives in molecular nano-spintronics is to manipulate the spin states of organic molecules with a d-electron center, by suitable external means. In this letter, we demonstrate by first principles density functional calculations, as well as second order perturbation thoery, that a strain induced change of the spin state, from S=1 → S=2, takes place for an iron porphyrin (FeP) molecule deposited at a divacancy site in a graphene lattice. The process is reversible in a sense that the application of tensile or compressive strains in the graphene lattice can stabilize FeP in different spin states, each with a unique saturation moment and easy axis orientation. The effect is brought about by a change in Fe-N bond length in FeP, which influences the molecular level diagram as well as the interaction between the C atoms of the graphene layer and the molecular orbitals of FeP.
@article{arxiv.1210.0666,
title = {Graphene as a reversible spin manipulator of molecular magnets},
author = {Sumanta Bhandary and Saurabh Ghosh and Heike Herper and Heiko Wende and Olle Eriksson and Biplab Sanyal},
journal= {arXiv preprint arXiv:1210.0666},
year = {2012}
}