MnxGe1-x dilute magnetic semiconductor studied by XAFS

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Fluorescence X-ray absorption fine structure (XAFS) technique was used to investigate the local structures of the doped Mn in the MnxGe1-x dilute magnetic semiconductors (DMSs) with different Mn content (x=0.07, 0.25, 0.36) prepared by magnetron cosputtering method. The results indicate that for the sample with low Mn content (x=0.07), the Mn atoms are mainly incorporated into the lattice of Ge, and locate at the substitutional sites of Ge atoms with the ratio of 75%. With the Mn content increasing to 0.25 or higher, only part of Mn atoms enter the lattice of Ge and the others exist in the form of the Mn5Ge3 phase whose content increases with the doped Mn concentration. It is found that, in the Mn0.07Ge0.93 the bond length of the first (Mn-Ge) shell is RMn-Ge = 2.50 Å, which is bigger than the first (Ge-Ge) shell distance in Ge by about 0.05 Å. These results imply that local structure expansion is induced by dilute Mn substituting into Ge sites.