  The integration of ferromagnetic Mn5Ge3 with the Ge matrix is promising for
spin injection in a silicon-compatible geometry. In this paper, we report the
preparation of magnetic Mn5Ge3 nanocrystals embedded inside the Ge matrix by Mn
ions implantation at elevated temperature. By X-ray diffraction and
transmission electron microscopy, we observe crystalline Mn5Ge3 with variable
size depending on the Mn ion fluence. The electronic structure of Mn in Mn5Ge3
nanocrystals is 3d6 configuration, the same as in bulk Mn5Ge3. A large positive
magnetoresistance has been observed at low temperatures. It can be explained by
the conductivity inhomogeneity in the magnetic/semiconductor hybrid system.
