Abstract
Nanoparticles of a cobalt-platinum (CoPt) alloy near equiatomic composition. dispersed in a surfactant-polymer matrix, are synthesized using aqueous phase laser ablation. The magnetization dynamics of these particles is examined in the framework of the superparamagnetic blocking phenomenon based on a log-normal size distribution. Our analysts reveals, in accordance with electron microscopy results, two size distributions which peak at 1.3 and 5.9 nm. The magnetic anisotropy energy of these particles is 0.9 x 10(6) Jm(-3) and 0.1 x 10(6) Jm(-3), respectively.