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Abstract:
Polycrystalline samples of the Heusler compound Co2TiSn have been
prepared and studied using bulk techniques (x-ray diffraction and
magnetization) as well as local probes (Sn-119 Mossbauer spectroscopy
and Co-59 nuclear magnetic resonance spectroscopy) in order to determine
how disorder affects the half-metallic behaviour and also to establish
the joint use of Mossbauer and NMR spectroscopies as a quantitative
probe of local atom ordering in these compounds. Additionally, density
functional electronic structure calculations on ordered and partially
disordered Co2TiSn compounds have been carried out at a number of
different levels of theory in order to simultaneously understand how the
particular choice of DFT scheme as well as disorder affects the computed
magnetization. Our studies suggest that a sample which seems well
ordered by x-ray diffraction and magnetization measurements can possess
up to 10% of antisite (Co/Ti) disordering. Computations similarly
suggest that even 12.5% antisite Co/Ti disorder does not destroy the
half-metallic character of this material. However, the use of an
appropriate level of non-local DFT is crucial.
