Enhanced coercivity in non-equiatomic CoPt-Cu nanoparticles

Co30Cu10Pt60 nanoparticles were prepared by a simplified polyol process devoid of any surfactants or capping agents. Thermo-magnetic analysis showed that the addition of 10 at.% Cu reduces the Curie temperature of Co40Pt60 from 492 °C to 435 °C. The incorporation of Cu is effective in reducing the threshold ordering temperature for the A1-fcc to L10-fct phase transformation of CoPt, resulting in coercivity enhancement. Coercivity close to 10 kOe at a lower annealing temperature of 600 °C in Co30Cu10Pt60 demonstrates that high coercivity in CoPt can be achieved in non-equiatomic compositions also. Annealing temperature dependent two phase behavior has been understood by δM studies.