Tailoring Structure and Magnetic Characteristics in L1₀-FePt Nanoparticles via Ag Doping in Different Valence States

FePt, FePtAg and FePt–AgCl nanoparticles (NPs) are synthesized using the sol–gel method. The effect of Ag in different valence states on the morphology, chemical ordering and magnetic properties of L1₀-FePt NPs are studied in length. The addition of Ag to FePt NPs results in a larger particle size and wider distribution. Magnetic measurement results show that the coercivity (Hc) of FePt NPs is significantly higher with the addition of Ag in comparison with that of pure FePt NPs. While Ag⁺ executes a negative impact on the magnetic performance of FePt NPs. The saturation magnetization (Ms) for the FePt, FePtAg and FePt–AgCl NPs are 15.6, 10.6 and 6.9 emu/g, respectively. The addition of non-magnetic Ag or AgCl to FePt dilutes the Ms value of the NPs. From X-ray diffraction analyses, we observe that the diffraction peaks become sharper and considerably increasing intensity when Ag or AgCl is added to the FePt sample.