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We use in-situ microscopy to observe deposition and growth of nanoscale materials while, simultaneously, imaging their magnetic structure. We illuminate sample surfaces with a spin-polarized beam of electrons and observe spin-dependent electron reflection to form images. The images contain information on sample structure as well as electronic and magnetic properties. This is interesting, both to shed light on basic magnetic phenomena and because the properties of small magnetic domains are potentially useful to enable miniaturization of spin-based devices. Several examples including self-assembled magnetic nanodots, self-organized nanowire arrays, and epitaxial multilayer structures will be discussed to show how SPLEEM can be used to study magnetism in low-dimensional systems.
We can also use the measurements of spin-dependent electron reflection from epitaxial thin films grown in-situ on magnetic substrates to determine the dispersion of unoccupied bands in the thin films. For example, in MgO/Fe(100) thin films we were able to determine two MgO energy bands with ?1 asymmetry. We find that a bulk-like MgO energy gap is fully established for MgO film thicker than 3 atomic monolayers, and that the electron reflectivity from the MgO/Fe interface exhibits a spin-dependent amplitude and a spin-independent phase change. Moreover, we find that SPLEEM images from non-magnetic overlayers reveal magnetic domains of the magnetic substrates. For example in the case of Cu films grown on fcc Co(100) layers, the domain contrast oscillates with electron energy and Cu film thickness. This observation can be attributed to the spin-dependent electron reflectivity at the Cu/Co interface, which leads to a spin-dependent Fabry-Pérot electron interference in the film.
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