Influence of F-ligands on Half-metallicity of Cubic Spinel Materials

O-ligands of Fe3O4 were substituted partly by F-ions, and then the magnetic and electronic properties of spinel compounds containing F-ligands were studied systematically based on the first principle calculation. Their electronic structures, and then the mechanisms of magnetic and electric properties were analyzed. It is shown that spinel materials have no half-metallicity if the O-ligands of Fe-ions on A-sites are substituted by F-ions. On the other hand, the concentration of F-ligands of Fe-ions on B-sites can cause a very important influence on the half-metallicity of spinel materials. There are no half-metallicity if x <= 0.5. If x > 0.5, materials have evidently half-metallicity. The Fermi level moves to higher energy, and then the half-metallicity are more stable with increasing concentration of F-ions. The main mechanism is that there is stronger crystal field with increasing concentration of F-ligands, which causes greater splitting of up-spin sub-bands. The electronic structures of a Fe-ion are Fe t(2g)(up arrow)(3)t(2g)(down arrow)(1)e(2)(up arrow)(g).