In this investigation, we delve into the precise synthesis of magnetic nanoparticles with a particular emphasis on the NiFe₂O₄ and CoFe₂O₄ ferrites, and the FeFe₂O₄ magnetite, employing a meticulously controlled chemical-synthesis methodology to ensure reproducibility and optimal material properties. To verify the chemical makeup and purity of these synthesized nanoparticles, we conduct the detailed characterization through energy-dispersive x-ray spectroscopy (EDX), which provides quantitative insights into their elemental composition. Leveraging these well-characterized nanoparticles as the foundational components, we formulate a series of magnetic fluids at diverse concentration levels, tailoring their rheological and magnetic behaviours for potential applications in fields such as biomedicine, electronics, and environmental remediation. Additionally, to assess comprehensively the thermoelectrical performance of these magnetic fluids, we perform systematic measurements of their electrical conductivity over an extensive temperature spectrum, thereby, elucidating how thermal variations influence their conductive characteristics and overall functionality under varying operational environments.