MBE growth and characterization of Ge1-xMnxTe ferromagnetic semiconductors

Abstract

We investigate the structural, magnetic and transport properties of Ge1b xMnxTe ferromagnetic semiconductor grown on BaF2 (111) substrate by solid-source molecular-beam epitaxy by varying the Mn composition from x = 0.14 to 0.98. X-ray diffraction shows that the Ge1b xMnxTe films crystallize in the NaCl phase for all x, whereas HRTEM shows the nonuniformity in the film. The dependence of Curie temperature TC on x tends to follow a quadratic behavior, which attributed to the increase of antiferromagnetic interaction. The observed Anomalous Hall effect of Ge1-xMnxTe thin film is the combination of the carrier-induced ferromagnetism with the effect of the clusters. The temperature-dependent resistivity measurement exhibits an upturn at low temperature which can be related to the ferromagnetic transition. The resistivity and M-T behaviors can be attributed to weak localization effect of disordering. The magnetoresistance (MR) of Ge1-xMnxTe displays very clear hysterestic loop at low temperature which reseumbles that of giant-magnetoresistance (GMR) granular system in solids. The negative MR behaviors may be accounted for the BMPs model.