MAGNETIC PROPERTIES RELY ON NUCLEATION AND GROWTH OF CORE-SHELL STRUCTURE NANOPARTICLES FORMED IN REVERSE MICELLE SOLUTION

This work is focused on the effect of reaction time on formation of nanoparticles by reversed micelles in the trimethylammonium bromide /n-octane/1-butanol extraction system. Adjusting the structural and morphological properties of the as-synthesized core-shell, cobalt-gold nanoparticles were highlighted and it is subsequently influences their magnetic properties. By employing controlled preparation conditions, the average crystalline size of the as-prepared samples was varied from 5 up to 20 nm. Configuration of single particles and clusters were reported by TEM and FESEM measurements. One of the significance of our work is to obtain high crystalline samples without applying any heat treatment. The degree of crystallinity of the as prepared samples was high like the ones after annealing. The room temperature magnetic measurements indicate that coercivity and remanence enhanced by increasing the particle size. Specifically, the as-prepared 8nm gold coated cobalt nanoparticles show very high coercivity, 1.175kOe, at room temperature. In addition the effect of annealing on structure and magnetic properties of Co-Au nanoparticles was studied.