A Hall coefficient investigation of ferromagnetic Ga 1− xMn xAs layers on (100) GaAs substrates

Abstract

Ferromagnetic Ga 1− x Mn x As epilayers with Mn mole fraction in the range of x≈2.2–4.4% were grown on semi-insulating (100) GaAs substrates using the molecular beam epitaxy technique. The transport properties of these epilayers were investigated through Hall effect measurements. The measured hole concentration of Ga 1− x Mn x As layers varied from 4.4×10 19 to 3.4×10 19 cm −3 in the range of x≈2.2–4.4% at room temperature. From temperature dependent resisitivity data, the sample with x≈4.4% shows typical behavior for insulator Ga 1− x Mn x As and the samples with x≈2.2 and 3.7% show typical behavior for metallic Ga 1− x Mn x As. The Hall coefficient for the samples with x≈2.2 and 4.4% was fitted assuming a magnetic susceptibility given by Curie–Weiss law in a paramagnetic region. This model provides good fits to the measured data up to T=300 K and the Curie temperature T c was estimated to be 65, 83 K and hole concentration p was estimated to be 5.1×10 19, 4.6×10 19 cm −3 for the samples with x≈2.2 and 4.4%, respectively, confirming the existence of an anomalous Hall effect for metallic and insulating samples.