Complex permeability studies of Li1+ substituted Cu-Zn ferrites

Compositions having the general formula Zn_0.5Cu_0.5−tLi_2tFe₂O₄, where t=0.00, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, and 0.1, have been synthesized by using coprecipitation techniques using oxalate precursors. The initial permeability was calculated from the inductance measurements with a torroidal core of 100 turns, using the formula L=0.0046 μ_i N² h log d₂/d₁. There is a decrease in initial permeability (μ_i) with the substitution of Li¹⁺ ions which is explained on the Globus model. The values of rotational permeability (μ_rk) and μ_w have been calculated. In all the compositions, the main contribution to the initial permeability is due to domain wall motion. With addition of Li¹⁺ ions the wall permeability μ_w decreases, which suggest that these ions cause impedance to the domain wall motion. The frequency variation of μ′ and μ″ clearly indicate the low-frequency dispersion which may be attributed to the domain wall movements. From the L.F. studies it is concluded that the losses are minimum in the frequency region of 10 KHz to 1 MHz as expected for lithium ferrites.