Low temperature magnetic hardening in self-assembled FePt/Ag core-shell nanoparticles

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 °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 °C, which is almost 100 °C lower than that of pure FePt nanoparticles. Negative peaks on the δM 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.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The core-shell structured FePt/Ag nanoparticles show a lower ordering temperature. ► FePt nanoparticles can obtain larger coercivities by coating Ag shells. ► Ag shells help to reduce the dipolar-type interaction between the annealed particles.