Applied Physics

Half Metal, Full Spin

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Science  03 Jul 2009:
Vol. 325, Issue 5936, pp. 13
DOI: 10.1126/science.325_13a

For optimal efficiency in spintronic applications (which replace ordinary charge flow with spin current), host materials should ideally be completely spin-polarized. Unfortunately, not many materials have this property. Heusler alloys constitute an emerging prospect. These are metals, or rather half-metals, in which the conduction band is split into two polarizations—one half occupied, the other empty—thus providing 100% spin polarized current transport. However, the materials studied so far have shown strongly temperature-dependent behavior due to the band structure, making them unsuitable for practical device applications. Shan et al. now show that Fermi-level tuning by the introduction of appropriate dopant atoms, a technique similar to electron or hole enrichment in semiconductors, can be applied to the Heusler alloy Co2FeAl0.5Si0.5. With a spin-polarization exceeding 90% and a weak temperature dependence up to room temperature, the resulting material highlights the potential of Fermi-level tuning for attaining high performance in spintronic applications.

Phys. Rev. Lett. 102, 246601 (2009).

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