Enhanced L10 phase transition in CoPt/Ag core/shell nanoparticles

We have prepared CoPt/Ag core/shell nanoparticles (NPs) by the seed-medium method and demonstrated that Ag shells perform a crucial role in the magnetic enhancement of CoPt NPs. The NPs were annealed under Ar+5%H2 atmosphere at different temperatures and the coercivities of both CoPt and CoPt/Ag NPs increase with the rise of annealing temperature. The room temperature coercivity of the CoPt/Ag NPs reaches 19 kOe after annealing at 650 °C, which is much higher than that of CoPt NPs (∼2880 Oe). From XRD patterns, the (001) and (110) peaks of the CoPt/Ag NPs are stronger than those of the CoPt ones, indicating a more complete L10 phase transition induced by Ag shells.

► CoPt/Ag core/shell nanoparticles have been prepared.
► Room temperature coercivity of CoPt/Ag NPs is as high as 19 KOe.
► A much complete L10 phase transition can be induced by Ag shells.