An experiment has shown that sulfur doping in graphene induces paramagnetic centers with localized spins in the graphene lattice. These spin-carrying centers behave independently of each other if the concentration of substituting sulfur is below the threshold level. Once the doping threshold is overcome, magnetic interactions mediated by the π-electron system evolve between the substitution-generated paramagnetic centers, establishing a ferromagnetic state with a Curie temperature. The emergence of the ferromagnetic state at low temperatures was theoretically confirmed by computational study identifying magnetically active configurations. The superior magnetic properties of the S-doped graphenes over the N-doped analogs can be explained in terms of injection of two unpaired electrons by each sulfur atom to the conducting band; these electrons are delocalized among the S and C atoms contrary to those injected by N-doping that are dominantly localized at the N sites. The pumping of electrons from substitutional sulfur to the graphene conduction band is also believed to promote the sustainability of the magnetism at relatively high temperatures. Finally, the magnetically ordered S-doped graphenes with a prominent saturation magnetization and coercivity offer viable highly conductive materials, which, if further functionalized, would display strengthened self-sustainable magnetism against thermal fluctuations with a huge potential in spintronics and other magnetic applications.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering