Ab initio studies of disorder in the full Heusler alloy Co FeMnSi

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Co-based full Heusler alloys have been predicted to be half-metals, with 100 spin polarisation at the Fermi level, yet this has yet to be realised in practice. Heusler thin-films often exhibit a degree of atomic disorder, and this is believed to be one cause of the low magnetoresistance in Heusler-based spin valves devices. We present an ab initio density functional theory U investigation into the effect of disorder on the electronic properties of CoFeMnSi. It is found that the half-metallicity depends strongly on the kind of disorder present, with low or even reversed spin-polarisation when the Co sublattice mixes with either the Fe/Mn or Si sublattice, but keeps the high spin polarisation when the Mn/Fe and Si sublattices are mixed. Calculations of the formation energy show that this latter kind of disorder is by far the most likely to occur, an encouraging result which means that it may not be necessary to produce perfectly ordered Heusler alloys in order to achieve 100 spin polarisation.
Original languageEnglish
Article number17B106
JournalJournal of Applied Physics
Issue number17
Publication statusPublished - 7 May 2013

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