Room-temperature ferromagnetism in single crystal Fe1.7Ge thin films of high thermal stability grown on Ge(111)

We report on the epitaxial growth of ultrathin ferromagnetic Fe1.7Ge layers on Ge(111) wafer. These single crystal intermetallic layers adopt the InNi2 (B8(2)) crystallographic structure. They are ferromagnetic with a Curie temperature well above room temperature. The interface between the ferromagnet layer and the Ge wafer is of high perfection. Interestingly, the annealing of the sample up to 300 degrees C alters neither the crystallographic structure, nor the interface quality, nor the magnetic properties but leads to a nearly perfect smoothening of the germanide layer surface. This high thermal robustness should open the way for the growth of fully epitaxial iron germanide/Ge hybrid structures. (C) 2008 American Institute of Physics.