Interlayer Exchange Coupling in Short Period GaMnAs/GaAs Superlattices

The low dimensional structures containing III-V ferromagnetic semiconductors were intensively investigated in the last few years because of the variety of their potential applications. The aim of the present work was to study the interlayer exchange coupling in the short period GaMnAs/GaAs superlattices containing 16 or 8 GaMnAs monolayers. Samples with the magnetic layers corresponding to the mixed crystal composition with 5% or 6% of Mn were grown by MBE technique and characterized by both high-resolution X-ray diffraction and Raman scattering methods. Folded acoustic phonons were observed for the first time for this particular quantum system in the Raman scattering spectra. The interlayer exchange coupling in selected superlattices was investigated by both elastic neutron scattering (diffraction) and polarized neutron reflectivity measurements. Presence of the smooth interfaces and the stability of the superlattice period were confirmed by neutron reflectometry data. Ferromagnetic correlation of the magnetization vector in subsequent GaMnAs magnetic layers was demonstrated by both experimental methods.