Studies of AC electrical conductivity and initial magnetic permeability of rare-earth-substituted Li-Co ferrites

In the present work, the AC electrical conductivity and initial magnetic permeability were investigated for some Rare-earth-substituted spinel ferrites. These ferrites are of composition Li0.5-0.5xCoxFe2.4-0.5xR0.1O4 (where x = 0.0, 0.5, and 1; R = Y, Yb, Eu, Ho and Gd). They were prepared by standard ceramic techniques. With respect to AC electrical conductivity, measurements show dispersion with frequency at low temperatures. This dispersion obeys the universal power law. The frequency exponent of the power law decreases with both Co ion content and temperature. This indicates that the classical barrier hopping mechanism is the predominant one in these samples. On the other hand, the behavior of the initial magnetic permeability with temperature exhibits multidomain structure only for the samples with x = 0.0, and single domain structure otherwise. (C) 2005 Elsevier B.V. All rights reserved.