The FePt/Ag core-shell nanoparticles with different Ag shell thickness have been fabricated using a seed mediated technique. The core-shell nanoparticles are annealed at temperatures ranging from 350 to 600 degrees C for 30 min in vacuum. The magnetic measurement demonstrates that the FePt/Ag core-shell nanoparticles show a better chemical ordering tendency with a magnetic hardening temperature of 400-450 degrees C, which is almost 100 degrees C lower than that of pure FePt nanoparticles. Negative peaks on the delta M curves of the annealed FePt/Ag core-shell nanoparticles demonstrate that the predominant interparticle interactions are dipolar type rather than exchange coupling one. Besides, the FePt/Ag core-shell nanoparticles show both sensitive plasmonic and superparamagnetic properties. The present results indicate that our composite nanoparticles are very promising from the viewpoint of the optoelectronics and biomedical applications. (C) 2011 Elsevier B.V. All rights reserved.