L1(0) ordered phase formation at solid state reactions in Cu/Au and Fe/Pd thin films

To understand the mechanism of mass transfer during solid state reactions and order-disorder transitions the formation processes of CuAuI and L1₀-FePd ordered structures at solid state reactions in Cu/Au и Fe/Pd bilayer thin films have been carried out using the method of in situ electron diffraction (ED). The value of the long-range order (LRO) parameter has been estimated for the L1₀ type ordered structures being formed; the order-disorder transition temperatures have been determined. The formation mechanism of the L1₀ type ordered structures formed at the initial stages of the solid state reaction in the Cu/Au and Fe/Pd thin films has been suggested. In the case of Cu/Au it has been shown that the interdiffusion of copper and gold at the initial stage of the solid state reaction results in the reduced size of the grains of the initial materials, as a result, nanocrystalites of the Cu-Au solid solution are formed, and further, grains of the CuAuI ordered solid solution appear and their growth begins.