Mechanism of strong ferromagnetism in GdN

GdN and EuO are found to be strong ferromagnets with similar values of T-c. They have similar electronic characteristics but have different 4f level positions and band gaps. Due to these differences, a mechanism for strong ferromagnetism in EuO is not applicable for GdN. Detailed theoretical investigation has been performed on the cross processes between the f-d mixing and the f-d exchange interactions, which are thought to give strong ferromagnetic exchange interaction. It is found that the mixing through 4f(8) configuration is important in GdN in good agreement with experimental results.