  We have investigated the electronic and magnetic response of a single Fe atom
and a pair of interacting Fe atoms placed in patterned dehydrogenated channels
in graphane within the framework of density functional theory. We have
considered two channels: "armchair" and "zigzag" channels. Fully relaxed
calculations have been carried out for three different channel widths. Our
calculations reveal that the response to the magnetic impurities is very
different for these two channels. We have also shown that one can stabilize
magnetic impurities (Fe in the present case) along the channels of bare carbon
atoms, giving rise to a magnetic insulator or a spin gapless semiconductor. Our
calculations with spin-orbit coupling shows a large in-plane magnetic
anisotropy energy for the case of the armchair channel. The magnetic exchange
coupling between two Fe atoms placed in the semiconducting channel with an
armchair edge is very weakly ferromagnetic whereas a fairly strong
ferromagnetic coupling is observed for reasonable separations between Fe atoms
in the zigzag-edged metallic channel with the coupling mediated by the bare
carbon atoms. The possibility of realizing an ultrathin device with interesting
magnetic properties is discussed.
