Origin of magnetization in diluted magnetic semiconductor GaGdAs monolayer and superlattice

In this study, monolayer (ML)- and superlattice (SL)-diluted magnetic GaGdAs semiconductors are fabricated, and their electronic states are analyzed by X-ray absorption spectrum (XAS) and magnetic circular dichroism (MCD) by comparing with the values observed in case of macroscopic magnetization. The Gd magnetic moment per atom that was obtained from MCD exhibited a lower value than that obtained from a superconducting quantum interference device (SQUID) and tended to be larger in the SL structure as compared to the ML structure. We further observed that the Gd magnetic moment was enhanced by more than several tens of mu(B) because of increasing carrier density by Si doping. The transmission electron microscopy images revealed dark regions with diameters of 2-3 nm, which were indicative of the high concentrations of Gd that further resulted in the formation of zincblend GaGdAs particles.