The knowledge of the magnetocrystalline anisotropy is often essential and its determination remains an ambitious challenge. In this article, we propose a new way to measure the anisotropy magnetic field of some substituted lithium ferrites. To achieve that, we have measured the complex permeability versus frequency of several substituted lithium-based ferrites, in which, the anisotropy field is related to the gyromagnetic resonance frequency. However, the gyromagnetic resonance frequency is hidden by the domain wall motion resonance. To solve the problem, we have sintered the ferrite at different temperatures to control the microstructure of the ferrite, thus separating the magnetization mechanisms. We have obtained results of anisotropy fields comparable to those of the literature between 270 and 460 Oe.