Growing thin magnetic films with a mask: Distinguishing between magnetic and instrumental asymmetries

A simple technique is presented which allows a very small spin polarization to be distinguished from a vanishing one in spin polarized scanning electron microscopy (spin-SEM). Ferromagnetic thin films are evaporated through a mask onto a nonmagnetic substrate, thus producing a patterned area. Spin polarization and the element specificity of the secondary electron yield are combined to determine a local]] asymmetry zero" where the spin polarization vanishes. With this technique it is possible to distinguish between a single domain thin film and a nonmagnetic one in spin-SEM. This is exemplified by monolayer Co/Cu (100) films.