[en] Substituted Li ferrites with chemical composition Li_{0.5+0.5t-0.5x}Fe_{2.5-1.5t-0.5x}Ti_tZn_xO₄, where t=0.55 and x=0.1, 0.2, 0.3 and 0.4 with additions of 0.005 Bi₂O₃ and 0.05 MnO₂ were synthesised by a ceramic method and selected parameters such as Curie temperature T_c, saturation induction B_s and coercivity H_c were measured and discussed. The complex permeability of prepared ferrites was measured in the frequency range of 1 MHz-1 GHz using impedance spectroscopy. The permeability spectra have shown the characteristic frequency dispersion and the contributions of relaxation and resonance effects to this dispersion are also discussed. The observed dispersion resulted from the contributions of the resonance-type of domain wall motion superimposed over the relaxation-type of wall displacements or magnetisation rotation. The detected resonance can be explained by the existence of demagnetising fields due to worse grain axis continuity