Structural and magnetic properties of GaGdN/GaN superlattice structures

GaGdN/GaN superlattices (SLs) having various GaGdN and GaN layer thicknesses were grown on Al2O3 (0001) substrates by radio frequency molecular beam epitaxy and their structural and magnetic properties were investigated. By changing the thickness of GaGdN and GaN layer in the GaGdN/GaN SL, we find that the lattice constant in the c-direction of GaGdN is larger than that of GaN. All SLs samples exhibited ferromagnetic characteristics at 10 K and 300 K. Comparing with the GaGdN single layer sample, the magnetization of SL samples is larger at the same unit volume of GaGdN. Magnetization data show that the SL samples having relatively thinner GaGdN layer and thicker GaN layer have larger magnetic moment per Gd atom. This phenomenon can be explained by considering that the carriers (electrons) flow from the GaN layers and are accumulated in the GaGdN layers; thinner GaGdN layer has higher carrier density, suggesting the carrier-enhanced magnetization in SL structure.