The investigation of dielectric properties under the application of varying frequencies provides a significantly enhanced understanding and determination of magnetic fluids’ relaxation and polarization processes, thereby enabling the prediction of their state and structure. Applying electric fields at different frequencies induces changes in the dielectric parameters of magnetic nanoparticles, a phenomenon observed using dielectric relaxation spectroscopy. This thesis focuses on examining the impact of thermal degradation on a sample of MOGUL magnetic fluid MF with a nanoparticle concentration of 0.6%, where the carrier medium is Mogul transformer oil, and colloidal stability is maintained by oleic acid (C18H34O2). The resulting dielectric quantities were analyzed, presenting graphical dependencies as a function of the applied frequencies.