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Abstract:
Ferromagnetic thin films of Heusler compounds are highly relevant for
spintronic applications owing to their predicted half-metallicity, that
is, 100% spin polarization at the Fermi energy. However, experimental
evidence for this property is scarce. Here we investigate epitaxial thin
films of the compound Co2MnSi in situ by ultraviolet-photoemission
spectroscopy, taking advantage of a novel multi-channel spin filter. By
this surface sensitive method, an exceptionally large spin polarization
of (93(-11)(+7)) % at room temperature is observed directly. As a more
bulk sensitive method, additional ex situ spin-integrated high energy
X-ray photoemission spectroscopy experiments are performed. All
experimental results are compared with advanced band structure and
photoemission calculations which include surface effects. Excellent
agreement is obtained with calculations, which show a highly spin
polarized bulk-like surface resonance ingrained in a half metallic bulk
band structure.
