Investigation of superlattices based on ferromagnetic semiconductor GaMnAs by planar Hall effect

Abstract

Two ferromagnetic semiconductor GaMnAs-based superlattices (SLs) were investigated by measuring the planar Hall effect (PHE) with the external magnetic field applied in the plane of the sample. The two GaMnAs/GaAs SLs differed only by the Be doping of the nonmagnetic GaAs spacer layers. Both SLs showed a typical two-step transition behavior in PHE field scans at 4.0 K, essentially the same as that normally observed on single GaMnAs ferromagnetic layers with two in-plane magnetic easy axes. As the temperature increased to 30 K, the behaviors of the PHE changed differently in the two SL samples. The PHE in the undoped SL can be described simply by the temperature dependence of the magnetic anisotropy within the film plane of a GaMnAs film. However, the Be-doped SL revealed a completely different behavior, showing a transition of magnetization with a negative coercive field. The observation of this feature in a ferromagnetic multilayer indicates the presence of spontaneous anti-parallel interlayer exchange coupling between the GaMnAs magnetic layers. (C) 2012 American Institute of Physics. [doi:10.1063/1.3678436]