  The investigation of interactions between magnetic nanotubes is complex and
often involves substantial simplifications. In this letter an analytical
expression for the magnetostatic interaction, taking into account the geometry
of the tubes, has been obtained. This expression allows for the definition of a
critical vertical separation for relative magnetization between nanotubes and
can be used for tailoring barcode-type nanostructures with prospective
applications such as biological separation and transport.
