Fluorine intercalated graphene: Formation of a two-dimensional spin lattice through pseudoatomization

A suspended layer made up of ferromagnetically ordered spins could be created between two- monolayer or multilayer graphene through intercalation. Stability and electronic structure studies show that, when fluorine molecules are intercalated between two mono/multilayer graphene, their bonds get stretched enough $(\ensuremath{\sim}1.9\text{--}2.0\phantom{\rule{0.16em}{0ex}}\AA{})$ to weaken their molecular singlet eigenstate. Geometrically, these stretched molecules form a pseudoatomized fluorine layer by maintaining a van der Waals separation of $\ensuremath{\sim}2.6\phantom{\rule{0.16em}{0ex}}\AA{}$ from the adjacent carbon layers. As there is a significant charge transfer from the adjacent carbon layers to the fluorine layers, a mixture of triplet and doublet states stabilizes to induce local spin moments at each fluorine site and in turn form a suspended two-dimensional spin lattice. The spins of this lattice align ferromagnetically with nearest-neighbor coupling strength as large as $\ensuremath{\sim}100\phantom{\rule{0.16em}{0ex}}\mathrm{meV}$. Our finite-temperature ab initio molecular dynamics study reveals that the intercalated system can be stabilized up to a temperature of 100 K with an average magnetic moment of $\ensuremath{\sim}0.6{\ensuremath{\mu}}_{B}/\mathrm{F}$. However, if the graphene layers can be held fixed, the room-temperature stability of such a system is feasible.