Effect of Zn Addition on the Reduction of the Ordering Temperature of FePt Nanoparticles

Abstract

Monodisperse FePt nanoparticles with an average size of 4.11 nm were successfully synthesized via chemical co-reduction of iron acetylacetonate, Fe(acac)3, and platinum acetylacetonate, Pt(acac)2, by 1,2hexadecanediol as a reducing agent. Also (FePt)87Zn13 nanoparticles with average size of 4.24 nm were synthesized using the same method. The structural and magnetic properties of the prepared samples were respectively studied by XRD, TEM and VSM. L10 FePt ordered phase is formed at lower annealing temperature by addition of Zn. The (FePt)87Zn13 nanoparticles starts ordering after annealing at 400 °C, whereas FePt nanoparticles at 400 °C are still disordered alloys with superparamagnetic behavior. Additive Zn is very effective in decreasing the ordering temperature and enhancing the chemical ordering in (FePt)87Zn13 particles, So that coercivity 5200 Oe was measured for (FePt)87Zn13 nanoparticles annealed at 500 °C, compared with 1800 Oe for samples without Zn. This reduction in ordering temperature significantly reduces FePt particle coalescence and loss in positional order.