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Half-metallic ferromagnets display a particular type of itinerant-electron magnetism as well as unusual electronic properties. They are metallic for one spin channel, and should be ideally insulating or semiconducting for the opposite one. However, correlation effects are always crucial in these materials as they introduce an incoherent spectrum in the gap which is pinned at the Fermi energy, so-called nonquasiparticle states. We present theoretical calculations and discuss the importance of these states in connection with tunneling-conductance spectroscopy measurements. We also present results for the ferrimagnetic full-Heuslers Mn2VAl alloy, in which non-quasiparticle states are located below the Fermi level, and should be detectable by spin-polarized photoemission. |
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