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 40Pt 60 sample annealed at 700 oC in N 2 atmosphere showed a room temperature coercivity of 8.4 kOe. The magnetic interactions present in the samples were studied using δM measurements. The evolution of high coercivity in the samples annealed at 700 oC showed that N 2 is a cheaper alternative to the existing reducing gas mixture.
KeywordsCoPt Polyol process Coercivity Annealing δM
The authors acknowledge the Department of Science and Technology (DST), Govt. of India for financial assistance through the FIST program (SR/FST/PSI-117/2007) and FAST track project (SR/FTP/ETA-11/2008). The authors also acknowledge Dr. S. Amirthapandian and the UGC-DAE-CSR facilities sanctioned to Kalpakkam node for the TEM measurements.