Correlation of structural and magnetic properties of ferromagnetic Mn-implanted Si1-xGex films

We present a comprehensive study relating the magnetic properties to structural properties of Mn+-implanted Si1-xGex films as a function of Ge content (x=0-0.5). Ferromagnetic ordering with three critical temperatures, T-B similar to 10-16 K, T-C1 similar to 650-780 K, and T-C2 similar to 825-860 K, are reported in this material system. Element specific x-ray absorption fine structure results show that the majority of the Mn ions are nonsubstitutional in all samples. The transmission-electron microscopy coupled with z contrast and chemical analysis reveals the presence of Mn-rich nanosized clusters including Mn4Si7 in Si-rich samples and Mn7Ge3 phases in Ge-rich samples. A composition transition occurred at x similar to 0.2-0.3, where we observe a change in bond lengths and defect structures. Additionally, an enhancement in magnetizations with an increase in both T-B and T-C1 as well as a conversion from n-type to p-type conduction are also detected. (c) 2008 American Institute of Physics.