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

Abstract

We present a comprehensive study relating the magnetic properties to structural properties of Mn+ -implanted Si1-x Gex films as a function of Ge content (x=0-0.5). Ferromagnetic ordering with three critical temperatures, TB ∼10-16 K, TC1 ∼650-780 K, and TC2 ∼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 Mn4 Si7 in Si-rich samples and Mn7 Ge3 phases in Ge-rich samples. A composition transition occurred at x∼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 TB and TC1 as well as a conversion from n -type to p -type conduction are also detected. © 2008 American Institute of Physics.