CATION DISTRIBUTION IN NIZN-FERRITE FILMS DETERMINED USING X-RAY-ABSORPTION FINE-STRUCTURE

We have applied extended x-ray absorption fine structure (EXAFS) spect roscopy to study the cation distribution in a series of spin-sprayed N iZn-ferrite films, Ni0.15ZnyFe2.85-yO4(y=0.16, 0.23, 0.40, 0.60). The Ni, Zn, and Fe EXAFS were collected from each sample and analyzed to F ourier transforms. Samples of Ni-ferrite, Zn-ferrite, and magnetite we re similarly studied as empirical standards. These standards, together with EXAFS data generated from the theoretical EXAFS FEFF codes, allo wed the correlation of features in the Fourier transforms with specifi c lattice sites in the spinel unit cell. We find that the Ni ions resi de mostly on the octahedral (B) sites whereas the Zn ions are predomin antly on the tetrahedral (A) sites. The Fe ions reside on both A and B sites in a ratio determined by the ratio of Zn/Fe. The addition of Zn displaces a larger fraction of Fe cations onto the B sites serving to increase the net magnetization. The fraction of A site Ni ions is mea sured to increase peaking at approximate to 25% for y=0.6. At higher Z n concentrations (y greater than or equal to 0.5) the lattice experien ces local distortions around the Zn sites causing a decrease in the su perexchange resulting in a decrease in the net magnetization. (C) 1996 American Institute of Physics.