Four Magnetic colloids containing superparamagnetic Fe3O4 nanoparticles coated with citric acid have been prepared by different methods. The samples were characterized using different techniques (XRD, FT-IR, and TEM). XRD showed the formation of nano Fe3O4 with inverse spinel structure. TEM image confirmed the formation of nano Fe3O4 ranged between 8 – 12 nm. The The physical tests have been performed on the prepared samples, in order to reveal their microstructural and rheological