Magnetic anisotropy of the Fe-SiO2 and Fe20Ni80-SiO2 granular solid measured using the magnetic relaxation method

Abstract

A method was reported by which the effective anisotropy of the Fe-SiO2 and Fe20Ni80-SiO2 granular solid can be measured using the magnetic relaxation equations. The pure Fe-SiO2 and Fe20Ni80-SiO2 granular solid samples were fabricated using a sol-gel method in which the nanoscale bcc structure Fe and fcc structure Fe20Ni80 particles are dispersed in the silica matrix. The average size of the metal particles in the two discussed Fe-SiO2 and Fe20Ni80-SiO2 granular solid samples are 10 nm and 8 nm, respectively. The obtained values of the effective magnetic anisotropy are in the order of the 106 erg/cm3 and almost independent with temperature from 80K to 300K for these granular solid samples. These values are far larger than the magnetocrystalline anisotropy for the bulk bcc structure Fe and fee structure Fe20Ni80. The larger stress magnetic anisotropy may result in these larger magnetic anisotropy for these granular solid samples. It was found that the effective magnetic anisotropy of the Fe-SiO2 granular solid is larger than that of the Fe20Ni80-SiO2 granular solid, which may result from the larger stress anisotropy in Fe-SiO2 granular solid than in Fe20Ni80-SiO2 granular solid and the reason is discussed. © 1996 IEEE.