  Using first-principles calculations, we examine the electronic and magnetic
properties of partially open zigzag carbon nanotube (CNT) superlattices. It is
found that depending on their opening degree, these superlattices can exhibit
multiple localized states around the Fermi energy. More importantly, some
electronic states confined in some parts of the structure even have special
magnetic orderings. We demonstrate that, as a proof of principle, some
partially open zigzag CNT superlattices are by themselves giant (100%)
magnetoresistive devices. Furthermore, the localized(and spin-polarized) states
as well as the band gaps of the superlattices could be further modulated by
external electric fields perpendicular to the tube axis, and a bias voltage
along the tube axis may be used to control the conductance of two spin states.
We believe that these results will open the way to the production of novel
nanoscale electronic and spintronic devices.
