Influence of metal–oxide interfaces on L12 ordering in Cu3Pd Original Research Article

A strong influence of the polarity on the degree of L12 order near interfaces between Cu3Pd and MnO has been observed. In situ TEM annealing at various temperatures was performed to re-establish the L12 ordering in Cu3Pd alloy containing MnO precipitates. Subsequently, high-resolution transmission electron microscopy was used to analyze the long-range order in Cu3Pd (L12) at parallel {0 0 2} and parallel {1 1 1} Cu3Pd–MnO interfaces. Analyses of the polar {1 1 1} interfaces in the 〈1 1 0〉 and 〈1 1 2〉 projection show a gradual disappearance of L12 order within the Cu3Pd with decreasing distance to these interfaces. The interesting point is that the L12 order dissolves over about 10 monolayers (MLs). In contrast, for the non-polar parallel {0 0 2} interface viewed along 〈1 0 0〉 no influence on the L12 order and APB structure, even close to the interface could be observed. Analytical TEM analysis revealed a small enrichment of Pd at the {1 1 1} Cu3Pd–MnO interface in the Cu3Pd ML nearest to the interface. This phenomenon is not considered responsible for the interfacial disorder extending over such a large length scale. Physical effects that cause the disordering at the polar interface are discussed. The conclusion of the analysis is that the dipolar contribution to the internal energy acts as an initiation of disordering along the MnO/Cu3Pd interface but that the configurational entropy determines the extension of the disordered area.