Polycrystalline samples of the half-metallic ferromagnet Heusler compound Co_2TiSn have been prepared and studied using bulk techniques (X-ray diffraction and magnetization) as well as local probes (^119Sn Mössbauer spectroscopy and ^59Co nuclear magnetic resonance spectroscopy) in order to determine how disorder affects half-metallic behavior and also, to establish the joint use of Mössbauer and NMR spectroscopies as a quantitative probe of local ion ordering in these compounds. Additionally,

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... ensity functional electronic structure calculations on ordered and partially disordered Co_2TiSn 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 affect 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 disordering. Computations similarly suggest that even 12.5 disorder does not destroy the half-metallic character of this material. However, the use of an appropriate level of non-local DFT is crucial.