Evolution of High Coercivity in CoPt Nanoparticles Through Nitrogen Assisted Annealing

The presence of H (2) along with an inert gas during annealing was considered as a prerequisite in achieving high coercivity in alloys such as FePt and CoPt nanoparticles synthesized through chemical methods. CoPt nanoparticles were synthesized using a one-step polyol process without using any surfactant and annealed at various temperatures in N (2) atmosphere. The magnetic properties of Co Pt-40 (60) sample annealed at 700 C-o in N (2) atmosphere showed a room temperature coercivity of 8.4 kOe. The magnetic interactions present in the samples were studied using delta M measurements. The evolution of high coercivity in the samples annealed at 700 C-o showed that N (2) is a cheaper alternative to the existing reducing gas mixture.