M.N. Danchevskaya, Yu.D. Ivakin, L.F. Martynova, G.P. Muravieva
3-rd International Conference on Solvothermal Reactions ICSTR-3, Bordeaux, July 19-23, 1999, p.67
ABSTRACT. Pure and doped fine crystalline barium hexaferrite (HFB) can be effectively used as a magnetic medium for vertical high density magnetic entry and storage of information. HFB crystals have the form of hexagonal platelets and the direction of magnetization is perpendicular to planes of platelets that meets the requirements to a material - carrier used for the creation of magnetic disks. The authors of the report carried out synthesis of HFB both in water vapor atmosphere and in liquid medium in the temperature range (200-400)± at pressures P H2O (9-26) ЬPя in laboratory autoclaves. The researches have shown that HFB with the best performances can be obtained by thermovaporous treatment of dry mixtures of precursors gamma-Fe2O3 with barium hydroxide or nitrate). As Fe - containing precursor alfa-FeOOH can be also used. The formation of HFB begins at the temperature about 200 ±. The magnetic properties of synthesized HFB can be improved by increasing the temperature of thermovapor treatment. The coercive forces of the HFB samples synthesized about 400 C changes to (1,7-2,0) Koe and specific saturation magnetization of nonoriented samples amounts to (50-60) emu/g. The HFB crystals with low coercive force (0,6-0,7) Koe were obtained by introduction of microadditives at the stage of their formation in water vapor atmosphere. The HFB crystals are hexagonal platelets with diameter near 1 mkm and thickness (0,1-0,2) mkm. This research was made with financial support of RFBR pr. 98-03-32645a.