Cationic exchange in nanosized ZnFe2O4 spinel revealed by experimental and simulated near-edge absorption structure

S. J. STEWART, S. J. A. FIGUEROA, J. M. RAMALLO LÓPEZ, S. G. MARCHETTI, J. F. BENGOA, R. J. PRADO, F. G. REQUEJO

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

American Physical Society

Año: 2007 vol. 75 p. 73408 - 73412

0163-1829

The nonequilibrium cation site occupancy in nanosized zinc ferrites
6–13 nm with different degree of inversion
0.2 to 0.4 was investigated using Fe and Zn K-edge x-ray absorption near edge spectroscopy
XANES and extended x-ray absorption fine structure, and magnetic measurements. The very good agreement between experimental and ab initio calculations on the Zn K-edge XANES region clearly shows the large Zn2+
A→Zn2+B transference that takes place in addition to the well-identified Fe3+B→Fe3+
A one, without altering the long-range structural order. XANES spectra features as a function of the spinel inversion were shown to depend on the configuration of the ligand shells surrounding the absorbing atom. This XANESapproach provides a direct way to sense cationic inversion in these Zn-containing spinel ferrites. We also demonstrated that a mechanical crystallization takes place on nanocrystalline spinel that causes an increase of both grain and magnetic sizes and, simultaneously, generates a significant augment of the inversion.