Electrical and magnetic properties of NiCrxFe2-xO4 spinel (0 ≤ x ≤ 0.6)

The spinel ferrite NiCrxFe2-xO4 system was synthesized under atmospheric pressure, and showed single spinel phase in the XRD pattern. The lattice parameter decreased with increasing amount of Cr. For the study of cation distribution in this system, magnetic measurements and Mossbauer spectroscopy were carried out. It was found that ions at the B site moved to the A site, and that this system varied from an inverse to a normal spinel structure. It was observed that the magnetic moment of the systems and Curie Temperature decreased by substitution effect. Using a thermopower measurement, this system was found to exhibit n-type semiconductivity. In the electrical conductivity measurements, an abrupt change exists near the Tc, owing to the magnetic spin arrangement relaxation. The electrical conduction mechanism of spinel is an electron transfer between the +2 and +3 cations at the B site, so called polaron hopping mechanism. From the conductivity result, this system is closely related to the electron-hole-compensation between electrons and holes. (C) 1999 Elsevier Science S.A. All rights reserved.