Co2MnGa0.5Sn0.5 (CMGS) thin films were epitaxially grown on MgO (0 0 1) substrates by magnetron sputtering and the current spin polarizations of the films with different post annealing conditions were measured by the point contact Andreev reflection method. The film deposited at a substrate temperature of 150 °C had a B2 structure and its spin polarization was estimated to be 59%. The film was ordered to the L2 1 structure by annealing at 600 °C, and the spin polarization was enhanced to 66%. The spin polarization and the intensity of the L21 diffraction showed clear correlation, suggesting L21 ordering is essential to achieve higher spin polarization of this quaternary Heusler alloy.
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