Crystallite size dependence on the magnetic properties of nanocrystalline magnetite powders

Single phase magnetite powders with crystallite sizes ranging from 8-50 nm were synthesised and studied using X-ray diffraction and Mossbauer spectroscopy. Lattice parameters were seen to decrease at very small crystallite sizes. Quadrupole splitting of the B sites increased with decreasing crystallite size before the spectrum collapsed into a doublet at the smallest sizes. These observations have been explained in terms of high surface-to-volume ratios in the small nanocrystals creating excessive lattice strain and large electric field gradients. (C) 1997 Elsevier Science B.V. All rights reserved.