  Hybrid Graphene/magnetic structures offer a unique playground for fundamental
research, and opportunities for emerging technologies. Graphene-spaced
ultrathin structures with antiferromagnetic exchange-coupling (AFC) seem a
relevant scenario, analogous to that of conventional metallic multilayer
devices. Unfortunately, the AFC found so far between bulk magnetic single
crystals and Graphene-spaced adatoms, clusters or molecules either requires low
temperatures, is too weak, or of complex nature, for realistic exploitation.
Here we show theoretically and experimentally that a strong perpendicular AFC
can be established in ultrahin-film structures such as Fe/Gr/Co on Ir(111),
first-time enabling Graphene-based synthetic antiferromagnet and ferrimagnet
materials with unprecedented magnetic properties and appearing suitable for
applications. Remarkably, the established AFC is robust on structure
thicknesses, thermally stable up to room temperature, very strong but
field-controllable, and occurs in perpendicular orientation with opposite high
remanent layer magnetizations. Our atomistic first-principle simulations
provide further ground for the feasibility of Graphene-mediated AFC ultra-thin
film structures, revealing that Graphene acts not only as mere spacer but has a
direct role in sustaining antiferromagnetic superexchange-coupling between the
magnetic layers. These results provide a path for the design of unique and
ultimately-thin synthetic antiferromagnetic structures, which seem exciting for
fundamental nanoscience studies or for potential use in Graphene-spintronics
applications.
