  Focused-ion-beam milling is used to fabricate nanostencil masks suitable for
the fabrication of magnetic nanostructures relevant for spin transfer torque
studies. Nanostencil masks are used to define the device dimensions prior to
the growth of the thin film stack. They consist of a wet etch resistant top
layer and an insulator on top of a pre-patterned bottom electrode. The
insulator supports a hard mask and gives rise to an undercut by its selective
etching. The approach is demonstrated by fabricating current perpendicular to
the plane Co/Cu/Co nanopillar junctions, which exhibit current-induced
magnetization dynamics.
