Ultrathin Fe films on single crystal and virtual Ge(0 0 1) substrates: Towards the control of magnetic properties

Ultrathin Fe films have been epitaxially grown at room temperature on standard single crystal Ge(0 0 1) substrates and virtual Ge/Si(0 0 1) substrates. Their magnetic and electronic properties have been investigated in situ by spin polarized inverse photoemission and magneto-optical Kerr effect. In both cases, the onset of ferromagnetism appears definitively at 3 ML, and the overall behavior is very similar in the case of standard and virtual substrates, so that the latter can be employed for growing high quality Fe/Ge/Si interfaces. All the films investigated display uniaxial anisotropy, which is explained in terms of the surface morphology induced by the preparation conditions.