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

TL;DR

This study combines experimental XANES spectroscopy and simulations to reveal non-equilibrium cation site occupancy and inversion phenomena in nanosized ZnFe2O4 spinels, linking structural and magnetic properties.

Contribution

It provides new insights into cation distribution and inversion mechanisms in nanosized zinc ferrites using combined experimental and computational approaches.

Findings

Zn2+ transference between A and B sites confirmed

XANES spectra depend on ligand shell configuration

Mechanical crystallization increases inversion and magnetic size

Abstract

The non-equilibrium 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 spectroscopy XANES and EXAFS, and magnetic measurements. The very good agreement between experimental and ab-initio calculations on the Zn K-edge XANES region clearly show 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 spinel compounds. 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.