Graphene as a reversible spin manipulator of molecular magnets

TL;DR

This paper demonstrates that strain in graphene can reversibly manipulate the spin states of an adsorbed iron porphyrin molecule, enabling control over its magnetic properties through external mechanical means.

Contribution

It introduces a method to reversibly change the spin state of a molecular magnet using strain in graphene, combining first principles calculations and perturbation theory.

Findings

Strain induces a reversible change in FeP spin state from S=1 to S=2.

Tensile and compressive strains stabilize different spin states with distinct magnetic orientations.

The spin manipulation is linked to changes in Fe-N bond length and molecular orbital interactions.

Abstract

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 $\to$ 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.