Robust Room Temperature Ferromagnetism In Cobalt Doped Graphene by Precision Control of Metal Ion Hybridization

Abstract

Graphene-based magnetic materials exhibit novel properties and promising applications in the development of next-generation spintronic devices. Modern synthesis techniques have paved the way to design precisely the local environments of metal atoms anchored onto a nitrogen-doped graphene matrix. Herein, it is demonstrated that grafting cobalt (Co) into the graphene lattice induces robust and stable room-temperature ferromagnetism. These comprehensive experiments and first-principles calculations unambiguously identify that the mechanism for this unusual ferromagnetism is π-d orbital hybridization between Co d xz and graphene p z orbitals. Here, it is found that the magnetic interactions of Co-carbon ions are mediated by the spinpolarized graphene p z orbitals, and room temperature ferromagnetism can be stabilized by electron doping. It is also found that the electronic structure near the Fermi level, which sets the nature of spin polarization of graphene p z bands, strongly depends on the local environment of the Co moiety. This is the crucial, previously missing, ingredient that enables control of the magnetism. Overall, these observations unambiguously reveal that engineering the atomic structure of metal-embedded graphene lattices through careful d to p orbital interactions opens a new window of opportunities for developing graphene-based spintronics devices.

Electronic and Magnetic Properties of Co‐Decorated Molecular Organic Network Adsorbed on Graphene

“…[ 46 ] The latter mechanism acts through the polarization of spins at carbon sites, mediating the exchange interaction of the Co atoms. [ 47 ] Regarding the direct interaction of Co atoms, although it is weak, ferromagnetic coupling is energetically favorable. [ 46 ]…”

“…Nevertheless, we can refer to similar experimental works. For instance, a recently published DFT‐experimental study [ 47 ] reported stable room‐temperature ferromagnetism in a graphene‐based structure where Co atoms are placed onto nitrogen‐doped graphene at a distance of 9 Å from each other.…”

“…[46] The latter mechanism acts through the polarization of spins at carbon sites, mediating the exchange interaction of the Co atoms. [47] Regarding the direct interaction of Co atoms, although it is weak, ferromagnetic coupling is energetically favorable. [46] Spacing between magnetic atoms and also their location on the two sublattices of graphene, in the context of its bipartite nature, are two crucial factors that should be taken into consideration.…”

Recent advances in magnetism of graphene from 0D to 2D

“…The magnetic mechanism was subsequently investigated by Paidi et al both experimentally and theoretically, indicating that the intensive hybridization between Co d xz orbitals and graphene p z orbitals plays an important role in inducing ferromagnetism and the magnetic interactions are mediated by spin-polarized graphene π bands. 88 The dependence of the electronic structure near the Fermi level on the local environment of Co atoms provides a new way for tuning magnetism at the atomic-level.…”

Scrolling reduced graphene oxides to induce room temperature magnetism via spatial coupling of defects

“…S15a, ESI †) show the emergence of the ferromagnetic phase, 7,12 while the increase of magnetization with the decrease of temperature at the low-temperature regions indicates that the paramagnetic phase simultaneously exists. 37 It is known that the ferromagnet could have a Curie temperature (T c ) of above 300 K. 38,39 The temperaturedependent magnetization (M-T) of the DR-rGO nanoscrolls-550 was evaluated at high temperatures (300-800 K) with a relatively low applied magnetic field (500 Oe) (Fig. S15b, ESI †).…”