Magneto-optical properties of group-IV ferromagnetic semiconductor Ge1−xFex grown by low-temperature molecular beam epitaxy

Abstract

Group-IV ferromagnetic semiconductor Ge1−xFex was grown by low-temperature molecular beam epitaxy without precipitation of ferromagnetic Ge–Fe intermetallic compounds. The ferromagnetism of Ge1−xFex films was investigated by magnetic circular dichroism (MCD). In particular, the influence of the Fe content (x=2.0%–17.5%) and growth temperature (100 and 200°C) on the ferromagnetism was carefully studied. The MCD measurements revealed that the overall spectral features reflecting the band structure of the Ge1−xFex films were identical with those in bulk Ge, and that the large spin splitting of the band structure was induced by the incorporation of Fe atoms into the Ge matrix, indicating the existence of s,p-d exchange interactions. The Ge1−xFex films showed ferromagnetic behavior and the ferromagnetic transition temperature linearly increased with increasing the Fe concentration. These results indicate that the epitaxially grown Ge1−xFex is an intrinsic ferromagnetic semiconductor.