Oxygen stoichiometry effects in spinel-type NiMn2O4-δ samples

We report the effects of oxygen stoichiometry in the structure and magnetic response of spinel-type NiMn2O4-delta polycrystalline samples controlled by heat-treatments in different atmospheric conditions. The post-annealed samples were analyzed by Scanning Electron Microscopy associated to X-ray Energy Dispersion Spectrometry, X-ray Photoelectron Spectroscopy and AC/DC magnetic measurements. Results indicate that the oxygen stoichiometry highly influences the magnetic interactions between the ferromagnetic, and antiferromagnetic sublattices in these compounds due to the presence of manganese in three possible valence states. (c) 2005 Elsevier Ltd. All rights reserved.