  Zigzag graphene nanoribbons patterned on graphane are studied using
spin-polarized ab initio calculations. We found that the electronic and
magnetic properties of the graphene/graphane superlattice strongly depends on
the degree of hydrogenation at the interfaces between the two materials. When
both zigzag interfaces are fully hydrogenated, the superlattice behaves like a
freestanding zigzag graphene nanoribbon, and the magnetic ground state is
antiferromagnetic. When one of the interfaces is half hydrogenated, the
magnetic ground state becomes ferromagnetic, and the system is very close to
being a half metal with possible spintronics applications whereas the magnetic
ground state of the superlattice with both interfaces half hydrogenated is
again antiferromagnetic. In this last case, both edges of the graphane
nanoribbon also contribute to the total magnetization of the system. All the
spin-polarized ground states are semiconducting, independent of the degree of
hydrogenation of the interfaces. The ab initio results are supplemented by a
simple tight-binding analysis that captures the main qualitative features. Our
ab initio results show that patterned hydrogenation of graphene is a promising
way to obtain stable graphene nanoribbons with interesting technological
applications.
