The influence of silica matrix on the crystal structure and high frequency performance of cobalt nanoparticles

Abstract

Cobalt–SiO 2 nanocomposites were successfully synthesized by chemical precipitation combined H 2 reduction method. The influence of SiO 2 matrix on the crystal structure and high frequency magnetic properties of cobalt nanoparticles was investigated. Amorphous SiO 2 layer, which is adhered to Co particle surface through Si–O–Co bonds, inhibits the growth of the nanoparticles and stabilizes the face-centered-cubic (FCC) structured Co. The FCC-cobalt/SiO 2 nanocomposites exhibit soft magnetic behavior with saturation magnetization ( M s ) about 125 emu/g and coercivity ( H c ) smaller than 100 Oe. The permeability spectra of Co/SiO 2 nanocomposites depend on the SiO 2 contents. When the SiO 2 content is greater than 8 wt%, the permeability spectra demonstrate notable high frequency characteristic, in which the real part μ′ of the permeability is almost independent of frequency and the imaginary part μ″ remains extremely low in high frequency range.