PhotoEmission Electron Microscopy (PEEM)

Photoemission Electron Microscopy or PEEM is an imaging technique that uses the secondary electrons emitted from a sample surface upon absorption of photons. For low-energy photons, like the ones coming from a laser or a mercury lamp, a chemical contrast can be obtained if elements with different workfunctions are present at the sample surface (typically, metallic islands on a semiconductor substrate). Synchrotron x-rays provide a direct chemical contrast using the element-selectivity of x-ray absorption edges or x-ray photoemission. Magnetic sensitivity can be added using circularly polarized x-rays, through the X-ray Magnetic Circular Dichroism (XMCD) effect. The element- and magnetic sensitivity of XMCD-PEEM makes it a very powerful technique for investigating magnetic multilayered systems, like they are used in magneto-electronic devices (spin-valves, magnetic random access memories). In these devices, where several ferromagnetic (FM) layers are separated by non-magnetic or antiferromagnetic spacer layers, the domain patterns in the two FM layers, as well as their correlation and interaction, can be observed separately [1,2,3].

Fe/MgO(001)
Magnetic domain image of 50 nm of Fe on MgO(001) (sample courtesy C.Tiusan, Nancy) taken with the french PEEM/LEEM instrument at ELETTRA (Italy). The field of view is about 15 ┬Ám.
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