Coercivity analysis in the Co-x/(SiO2)(100-x) nanoparticulate system

We have prepared, by using a high-energy ball mill, samples consisting of C o nanoparticles (average diameters in the range from 7 up to 15 nm) dispers ed in SiO2. The coercivity of these samples has been measured as a function of the Co volume percentage, the milling time and the temperature. Our res ults show that, at temperature above 100 K, the coercive force depends on t emperature according to the law corresponding to isotropic uniaxial superpa ramagnetic particles. Below 100 K the occurrence of interparticle interacti ons originate measurable departures from that law. (C) 1999 Elsevier Scienc e B.V. All rights reserved.