Towards Design of High Spin Metal-free Materials

Abstract

In this paper, in order to explore high-spin carbon-based magnetic materials with strong ferromagnetic coupling, geometric structure, electronic structure and magnetic properties of alternating stacks of $\pi$-radical-halogenated-hydrocarbons and diamagnetic molecules have been investigated based on density-functional theory with dispersion correction. These alternating stacks are predicted to avoid the typical antiferromagnetic spin-exchange of indentical face-to-face radicals via spin polarization of a diamagnetic molecule in between. Our results show that $\pi$-radical-halogenated-hydrocarbons like perchlorophenalenyl (C$_{13}$Cl$_{9})$ is strong ferromagnetic coupling if alternatingly stacked with aromatics like fluorinated coronene (C$_{24}$F$_{12})$ or coronene (C$_{24}$H$_{12})$, while fluorinated perinaphthenyl (C$_{13}$F$_{9})$ and perinaphthenyl (C$_{13}$H$_{9})$ are not an equally good choice. The role of ligand configuration in determining exchange coupling in stacks is discussed. These results would give some hints for designing new high-spin carbon-based ferromagnetic materials.