Coercivity analysis in the Co x /(SiO 2 ) 100~x nanoparticulate system

We have prepared, by using a high-energy ball mill, samples consisting of Co nanoparticles (average diameters in the range from 7 up to 15 nm) dispersed in SiO 2 . The coercivity of these samples has been measured as a function of the Co volume percentage, the milling time and the temperature. Our results show that, at temperature above 100 K, the coercive force depends on temperature according to the law corresponding to isotropic uniaxial superparamagnetic particles. Below 100 K the occurrence of interparticle interactions originate measurable departures from that law. ( 1999 Elsevier Science B.V. All rights reserved.