Magnetic Properties of Colloidal Magnetite Solutions Stabilized with a Double Layer of Surfactants in Water

A series of seven samples of water-based magnetic fluid stabilized with a double surfactant layer was synthesized. The magnetic properties of the synthesized samples were determined as a function of their concentration. The obtained concentration dependences of the initial static magnetic susceptibility for all samples are described by a third-degree polynomial of the Langevin susceptibility with a negative cubic term, which contradicts the existing theoretical models.