Formation of L10-FePt nanoparticles with the precursor of [(Fe/Pt/Fe)/Ag]n multilayer at lowered annealing temperature

Microstructure and magnetic properties of [(Fe/Pt/Fe)/Ag]n multilayer films after ex situ annealing at various temperatures have been investigated. The results indicate that, the multilayer starts to transform to isolated L10-FePt nanoparticles embedded in Ag matrix after annealing at temperatures above 400℃ . The formation of the face_center tetragondal (fct) phase at relatively low tem peratures seems to relate with the rapid diffusion at the interface of "Fe/Pt/Fe " and the defects caused by Ag, and the high migration speed as well as the much smaller surface free energy of Ag leads to the separation of FePt nanoparticles , which is evidenced by the result of ΔM measurements.