Nature Commun. 5, 3974 (2014)

The spintronics community has been searching for materials exhibiting half-metallicity for a number of years: the prospect of a material that conducts for one spin orientation but is insulating or semiconducting for the other has remarkable technological potential. Several Heusler alloys — intermetallic compounds that crystallize in a Heusler phase — have been predicted to be half-metallic at room temperature, but experimental evidence for such behaviour is scarce. Now, Martin Jourdan and colleagues have demonstrated the half-metallicity of a Heusler-alloy thin film.

Using in situ ultraviolet photoemission spectroscopy, the authors measured a spin polarization of approximately 93% at the Fermi energy at room temperature in epitaxial Co2MnSi films. Combined with band-structure calculations, these results provide the first direct observation of half-metallicity in the surface region of a Heusler compound.

Unlike conventional estimates that are based on transport measurements, this technique provides a direct probe of the spin polarization. Therefore, these results not only pave the way for more powerful spintronic devices but also raise questions about the suitability of using such transport measurements for determining a material's half-metallicity.