Room Temperature Superparamagnetic Order with Colossal Magnetocrystalline Anisotropy in Aminoferrocene-based Graphene Molecular Magnets

Intensive studies are available on graphene-based molecular magnets due to their remarkable electric, thermal and mechanical properties. However, to date, most of all produced molecular magnets are ligand based and subjected to challenges regarding the stability of the ligand(s). The lack of long-range coupling limits high operating temperature and leads to short-range magnetic order. Herein, we introduce aminoferrocene-based graphene system with room temperature superparamagnetic behavior with long-range magnetic order that exhibits colossal magnetocrystalline anisotropy of 8 x10⁵ and 3x 10⁷ J/m³ in aminoferrocene and graphene-based aminoferrocene respectively. These values are comparable and even two orders of magnitude larger than the pure iron metal. Synthesized aminoferrocene [C₁₀H₉FeN]⁺ was reacted with graphene oxide prepared by the modified Hammers method and the chemical structure was characterized and confirmed by XRD, FT-IR, and Raman spectroscopy. To model the behavior of the aminoferrocene, we used density functional theory by placing the aminoferrocene molecule between two highly ordered hydroxylated sheets and allowing the structure to relax. The strong bowing of the isolated graphene sheets suggests that the charge transfer and resulting magnetization could be strongly influenced by pressure effects. In contrast to strategies based on ligands surface attachment, our present work opens new routes for future molecular magnets as well as the design of qubit arrays and quantum systems.