  We study by density functional and large scale tight-binding transport
calculations the electronic structure, magnetism and transport properties of
the recently proposed graphene ribbons with edges rolled to form nanotubes.
Edges with armchair nanotubes present magnetic moments localized either in the
tube or the ribbon and metallic or half-metallic character, depending on the
symmetry of the junction. These properties have potential for spin valve and
spin filter devices with advantages over other proposed systems. Edges with
zigzag nanotubes are either metallic or semiconducting without affecting the
intrinsic mobility of the ribbon. By varying the type and size of the nanotubes
and ribbons offers the possibility to tailor the magnetic and transport
properties, making these systems very promising for applications.
