Magnetic and electrical properties of MBE-grown (Ge1−xSix)1−yMny thin films

The polycrystalline (Si1−xGex)1−yMny thin films have been grown by using MBE and investigated. In Si1−xMnx and Ge1−xMnx alloy, Ge3Mn5 and SiMn phases are representative strong ferromagnetic phases. Ge3Mn5 are mainly formed when Ge is rich, and SiMn are mainly formed when Si is rich. These formations of specific phases are provable from structure analysis by X-ray diffractometer (XRD) and measuring magnetic properties by magnetic properties measurement system (MPMS). At low Ge composition, saturation magnetization values and Curie temperature generally increase with Ge composition. Ferromagnetic properties of polycrystalline (Si1−xGex)1−yMny thin films near RT disappear when amounts of Si become over 70at.% in Si1−xGex alloy because Ge3Mn5 phase that have Tc around 310K cannot be formed. It is confirmed that structural analysis shows that Ge is incorporated interstitially in the SiMn phase structure with a lattice expansion with respect to the original compound. But, definite properties change can not be observed. Hall measurement shows that polycrystalline (Si1−xGex)1−yMny thin films have p-type. Temperature dependency resistivity of (Si1−xGex)1−yMny thin films behavior like metal. However, there exist some transition points in resistivity curve that are relation with Curie temperature of magnetic phases.