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

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

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

APS

Año: 2006

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 XANES approach 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.