  High coercivity magnets are an important resource for renewable energy,
electric vehicles and memory technologies. Most hard magnetic materials
incorporate rare-earths such as neodymium and samarium, but the concerns about
the environmental impact and supply stability of these materials is prompting
research into alternatives. Here, we present a hybrid bilayer of cobalt and the
nano-carbon molecule C60 which exhibits significantly enhanced coercivity with
minimal reduction in magnetisation. We demonstrate how this anisotropy
enhancing effect cannot be described by existing models of molecule-metal
magnetic interfaces. We outline a new form of magnetic anisotropy, arising from
asymmetric magneto-electric coupling in the metal-molecule interface. Because
this phenomenon arises from pi-d hybrid orbitals, we propose calling this
effect pi-anisotropy. While the critical temperature of this effect is
currently limited by the rotational degree of freedom of the chosen molecule,
C60, we describe how surface functionalisation would allow for the design of
room-temperature, carbon based hard magnetic films.

Applied Physics;Materials Science