Long range Mn segregation and intermixing during subsequent deposition of Ge capping layers on Mn5Ge3/Ge(111) heterostructures

We report on the Mn segregation and diffusion during the epitaxial overgrowth of Ge on Mn5Ge3/Ge(111) heterostructures. It is shown that the underneath Mn5Ge3 layers remain stabilized at the interface with the substrate while a small amount of Mn can leave the layers and floats at the Ge growth front. Mn can then act as a surfactant during Ge growth along the (111) orientation. The Mn segregation length and also the state of Mn atoms incorporated in the Ge layers are found to depend on the growth temperature. At a growth temperature of 250 °C, a segregation length of ~ 10 nm is observed and Mn atoms incorporated in the Ge layers are uniformly distributed. At 450 °C, segregated Mn atoms can react with Ge to form Mn5Ge3 clusters inside the Ge overgrown layer. Such Mn5Ge3 clusters display random orientations and induce modification of the magnetic anisotropy of the whole film.