Mn5Ge3 compound, with its room-temperature ferromagnetism and possibility to epitaxially grow on Ge, acts as a potential spin injector into group-IV semiconductors. However, the realization of Ge/Mn5Ge3 multilayers is highly hampered by Mn segregation toward the Ge growing surface. Here, we show that adsorption of some monolayers of carbon on top of the Mn5Ge3 surface prior to Ge deposition allows to greatly reduce Mn segregation. In addition, a fraction of deposited carbon can diffuse down to the underneath Mn5Ge3 layers, resulting in an enhancement of the Curie temperature up to ∼360 K. The obtained results will be discussed in terms of the formation of a diffusion barrier by filling interstitial sites of Mn5Ge3 by carbon.

Structural and magnetic characterizations have been combined to investigate the growth kinetics of Ge 1−x Mn x diluted magnetic semiconductors (DMSs) on Ge(001) substrates by means of molecular beam epitaxy (MBE). We have identified the growth process window allowing stabilization of a high Curie temperature (T C ) nanocolumn phase and provide evidence that the growth of semiconducting Ge 1−x Mn x nanocolumns and metallic Mn 5 Ge 3 clusters is a competing process. Due to a continuous increase of the Mn concentration inside nanocolumns, induced by Mn segregation along the growth direction from the interface toward the film surface, nanocolumns become unstable when the Mn concentration reaches a value of ∼40 at.% then transform into Mn 5 Ge 3 clusters. We propose a real-time approach to realize stacked layers consisting of nanocolumns separated by a Ge barrier layer, allowing exploitation of the effect of giant magneto-resistance in multilayer structures