Ordered Phase Formation in Sm-Ni Thin Film Grown on Cu(111) Underlayer

摘要

Sm_xNi_(100-x) thin films are prepared on Cu(111) underlayers hetero-epitaxially grown on MgO(111) single-crystal substrates at 500 °C by ultra-high vacuum molecular beam epitaxy with varying the Sm composition from Ni rich to Sm rich region including SmNi_5 stoichiometry (x = 13-37 at. % Sm). The influence of film composition on ordered phase formation is studied by reflection high energy electron diffraction and X-ray diffraction. Sm-Ni(0001) epitaxial films with CuCu_5-type structure are obtained for the investigated compositional range. The epitaxial films consist of two ordered-phase variants whose orientations are rotated around the film normal by 30° each other. Cu atoms diffuse from the underlayer into the Sm-Ni film and substitute the Ni sites in SmNi_5 structure forming an alloy compound of Sm(Ni,Cu)_5. The Cu concentration in Sm(Ni,Cu)_5 phase increases with increasing the Sm composition. Cu atom diffusion into Sm-Ni film is assisting the formation of ordered phase.