The magnetic behaviour of nanostructured zinc ferrite

We have investigated a series of nanostructured ZnFe2O4 samples produced by mechanical activation (mean particle sizes d similar to 50-8 nm) by variable temperature neutron diffraction measurements (2-535 K) supported by DC magnetisation measurements (4.2-300 K). The systematic increase in the mean inversion parameter (c similar to 0.04-0.43) with increasing milling time is accompanied by a gradual decrease in the occurrence of the long range antiferromagnetic ordering observed in the starting ZnFe2O4 material, as well as a gradual decrease in the related diffuse short range order peak. The neutron diffraction patterns of particles with d < similar to 15 nm and c >similar to0.2 are consistent with the occurrence of ferrimagnetic order and exchange interactions of the type Fe3+(A)-O-2-Fe3+ [B]. Diagrams summarising the magnetic regions of nanostructured ZnFe2O4 are presented. The magnetic behaviour overall agrees well with the enhanced magnetisation and ferromagnetic behaviour reported for nanostructured, ultrafine and thin films of ZnFe2O4 by other groups using mainly magnetisation and Mossbauer spectroscopy measurements. (C) 2004 Kluwer Academic Publishers.