Electrical conductivity and magnetic properties of Li0.5Fe2.5-xCrxO4 ferrite

Cr-substituted lithium ferrite of different composition (Li0.5Fe2.5-xCrxO4) were prepared for x=0.0-1.0 by conventional ceramic technique. A structure characterization of all the samples was carried out by the X-ray diffraction technique and found that the lattice parameter decreases with increasing of Cr-substituted concentration. Magnetic properties such as permeability and quality factor were measured in the frequency range of I kHz to 100 MHz. The permeability and quality factor of Cr-substituted lithium ferrite were strongly affected by Cr-substituted concentration. The permeability decreased gradually from mu (f = 10 MHz) = 34.9 for Li0.5Fe2.5O4 to mu(f = 10 MHz) = 4.0 for Li0.5Fe1.5Cr1.0O4. The electrical conductivity and activation energy were measured by the DC two probes technique. The temperature dependence of DC conductivity shows the semiconductor nature. A change of slope in the Arrhenius plot (log sigma T vs. 10(3)/T) may be due to the ferri to paramagnetic transition. The conductivity variation shows two different regions with a large variation in the activation energy. The activation energies in the ferromagnetic region are greater than those in the paramagnetic region. (C) 2009 Elsevier B.V. All rights reserved.