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Intensive studies are published for 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 subject to challenges regarding the stability of the ligand(s). The lack of long-range coupling limits high operating temperature and leads to a short-range magnetic order. Herein, we introduce an aminoferrocene-based graphene system with room temperature superparamagnetic behavior in the long-range magnetic order that exhibits colossal magnetocrystalline anisotropy of 8 × 105 and 3 × 107 J/m3 in aminoferrocene and graphene-based aminoferrocene, respectively. These values are comparable to and even two orders of magnitude larger than pure iron metal. Aminoferrocene [C10H11FeN]+ is synthesized by an electrophilic substitution reaction. It was then reacted with graphene oxide that was prepared by the modified Hammers method. The phase structure and functionalization of surface groups were characterized and confirmed by XRD, FT-IR, and Raman spectroscopy. To model the behavior of the aminoferrocene between two sheets of hydroxylated graphene, we have 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 that uses interlayer intercalated aminoferrocene opens routes for future molecular magnets as well as the design of qubit arrays and quantum systems.

Herein, we report on the evolution of superparamagnetic behavior of Nb–Cr–Ta–V–W refractory high entropy alloy (RHEA) nanoparticles synthesized by a facile mechanical pulverization (high-energy ball milling) technique. Detailed X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) analyses have been made to evaluate the structure, morphology, compositional, and elemental distribution characteristics of RHEA nanoparticles and further compared with the bulk. XRD and SEM data coupled with EDS analyses indicate that the nano-RHEA retains the parent crystal structure and phase, but the size dramatically decreases with milling time. The average crystallite size decreases from ∼32 to ∼12 nm with an increasing milling time to 16 h. While the bulk samples exhibit diamagnetic behavior, interestingly, RHEA nanoparticles demonstrate superparamagnetic nature. Magnetic measurements, in both room temperature and cryogenic conditions, provide evidence of the temperature-independent superparamagnetic nature of the RHEA nanoparticles. Furthermore, the saturation magnetization value exponentially increased with milling time and stabilized after 8 h of pulverization, whereas the magnetic domain size followed an opposite trend. We believe drastic reduction in the magnetic domain size is responsible for this unusual and unexpected superparamagnetic pattern of the RHEA nanoparticle, which opens up a new route for low-cost magnetic applications under harsh environment conditions.