MAGNETIC NANOCOMPOSITES BY REACTION MILLING

Systems of small magnetic particles embedded in a nonmagnetic matrix were prepared by high energy ball milling. Besides carefully chosen milling conditions, in situ chemical reactions were used to control the properties of the product. Nanocomposites of iron particles in metal oxides (Al2O3 and ZnO), and magnetite particles in copper metal were prepared by reaction milling. The samples were characterized by X-ray diffraction and magnetic methods. A few hours of ball milling resulted in the completion of most chemical changes. Iron nanoparticles were formed with lattice strains of about 0.005; coercivities up to 400 Oe were achieved The magnetization of the iron particles is 25-40% less than that expected for bulk iron.