Iron overlayer polarization enhancement technique for spin-polarized electron microscopy

Abstract

Thin iron overlayers on ferromagnetic samples are shown to be nonintrusive probes of the magnetization of the underlying sample when using spin-polarized secondary-electron emission for domain microscopy. Domain images of the iron overlayer show that the local magnetization direction is indicative of that in the sample. The magnitude of the spin polarization, however, reflects the magnetization of the iron overlayer. Thus, for materials with low spin polarization, the iron overlayer provides a large signal enhancement. The method is also applicable to oxidized transition-metal surfaces. The iron film is found to be exchange coupled to the substrate across oxide layers on the sample surface. These points are demonstrated in experiments with an Fe〈100〉 whisker and with a Co-Ni alloy magnetic disk.