Metastable Sm(Fe,Cu)_5 ordered alloy films formed on Cu(111) underlayers

摘要

Sm-Fe thin films are prepared on Cu(lll) underlayers hetero-epitaxially grown on MgO(111) single-crystal substrates by using an ultra-high vacuum molecular beam epitaxy system. The. Sm/Fe composition is varied from Fe-rich (10 at. % Sm - Fe) to Sm-rich (30 at. % Sm - Fe) region including SmFe_5 stoichiometry. The influence of film composition on the film structure is studied by in-situ reflection high- energy electron diffraction and X-ray diffraction. Metastable Sm(Fe,Cu)_5 ordered phase formation is recognized in the Sm-Fe films with the investigated compositions. Cu atoms diffuse from the underlayer into the Sm-Fe film and substitute the Fe site in SmFe_5 structure forming an alloy compound of Sm(Fe,Cu)_5. The Sm-Fe films with Fe-rich compositions consist of Sm(Fe,Cu)_5 and bcc-Fe phases, whereas the Sm-Fe films with Sm-rich compositions consist of Sm(Fe,Cu)_5 and amorphous phases. Cu atom diffusion into Sm-Fe film is assisting the formation of ordered phase.