Studies of polycrystalline cobalt-substituted lithium ferrites

The lattice constant, density, electrical conductivity, activation energy, carrier concentration, mobility, Seebeck coefficient, and ferromagnetic resonance linewidth were studied on a series of cobalt-substituted lithium ferrites. We have found that all the samples studied have single phase spinel structure. The lattice constant and the density are increased with substituting Co²⁺ contents. All the specimens studied have two regions of different activation energies. In the region below T_a (below 220°C), the conduction is attributed to electron hopping from Fe²⁺ to Fe³⁺; and in the region above T_a (above 220°C), it is attributed to ionic diffusion of Li ion. The change of mobility is caused by the dispersion of ions. The ferromagnetic resonance (F.M.R.) experimental results indicated that cobalt substitution affects linewidths and relaxation frequency, but it does not affect the g-factor