Multiple phases in sputtered Cr2CoGa films

By magnetron co-sputtering, thin films of a nominal Cr2CoGa compound were deposited on MgO and MgAl2O4. To achieve crystallisation in the inverse Heusler structure, different heat treatments were tested. Instead of the inverse Heusler structure, we observed phase separation and precipitate formation in dependence on the heat treatment. The main precipitate is Cr3Ga in A15 structure. The remainder forms Co-rich CoGa in the B2 structure and possibly Cr-rich CoCr in the sigma-phase.