Synthesis and surface modified hard magnetic properties in Co0.5Pt0.5 nanocrystallites from a rheological liquid precursor

► A modified polyol process is reported for the synthesis of Co-Pt nanoparticles. ► Different particle sizes were obtained by varying the order of addition. ► Effect of particle size on fcc to fct phase transformation is discussed. ► Effect of heat treatments on evolution of magnetic properties is reported. ► Fully transformed Co-Pt nanoparticles resulted in a coercivity of 11.310 kOe.