Polarized neutron reflectometry studies of GaMnAs/GaAs superlattices

Polarized neutron reflectometry has been used to investigate details of spin ordering in ferromagnetic (FM) GaMnAs/GaAs superlattices. The reflectivity spectra measured below the Curie temperature reveal additional magnetic contributions to the structural superlattice Bragg peaks, clearly indicating the existence of FM interlayer correlations. Closer investigation of the magnetic reflectivity maxima using a full polarization analysis provides direct evidence that the FM order in the GaMnAs layers is truly long-range. Moreover, as shown by the data, the system exhibits a strong tendency of forming a single-domain FM arrangement, even when cooled through TC in zero external field.