Magnetic gels are a new class of soft polymer materials with the properties controlled by magnetic field. The structure of the magnetic gel is schematically represented in Figure 1.

Fig.1. Schematic representation of magnetic gel: 1-magnetic nanoparticle, 2- chemical cross-links, 3-polymer chains.

Method of the preparation of the magnetite nanoparticles in a matrix of poly(acrylamide) gel was developed. Synthesis of magnetic spinel iron oxide Fe₃O₄ in the matrix of polyacrylamide gel have been performed through coprecipitation of Fe(II) and Fe(III) in alkaline media. The reaction of coprecipitation in the polymer matrix was made at the different concentration of the iron salt mixture and at the different ratio Fe(II)/Fe(III). Electronography shows that the crystalline lattice of the particles is determined as a magnetite. The average size of the particles, d calculated from the half-width of the diffraction peak d ~ 20 nm. The morphology of the magnetite nanoparticles are characterized by transmission electron microscopy. The analyses of the compositions of the gels prepared with different amount of acrylamide and of the cross-linker shows that the weight fraction of magnetite in the gels is proportional to the mass of salt solution in the gel before the reaction with alkali. SAXS data demonstrates a marked difference in the size distribution of magnetic particles in the gels with different structure.