Abstract
We present, herein, an extended study of the half-Heusler alloy NiMnSb, starting with thedeposition technique, continuing with the basic structural and magnetic properties of thethin films, and finishing with the electronic and compositional properties of their surfaces.The experimental methods we apply combine magnetization and magnetoresistivitymeasurements, atomic force microscopy, ferromagnetic resonance, x-ray and neutrondiffraction, low energy electron diffraction, angle resolved x-ray photoemission, extendedx-ray absorption fine structure spectroscopy, soft x-ray magnetic circular dichroism andspin polarized inverse photoemission spectroscopy. We find that stoichiometric surfacesexhibit close to 100% spin polarization at the centre of the surface Brillouin zone at theFermi edge at ambient temperatures. There is strong evidence for a moment reorderingtransition at around 80 K which marks the crossover from a high polarization state(T<80 K) to a more representative metallic ferromagnetic state(T>80 K). The results from the different experimental techniques are successively reviewed, withspecial emphasis on the interplay between composition and electronic structure of theNiMnSb film surfaces. Surface segregation, consistent with a difference in free enthalpybetween the surface and the bulk, is induced by annealing treatments. This surfacesegregation greatly reduces the surface polarization.
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