Magnetic properties of FePt nanoparticles annealed with NaCl

Abstract

FePt nanoparticles have the potential to extend the data density of magnetic recording beyond 1 Tbit/in 2 . The phase transformation from low anisotropy, face-centered cubic to face-centered tetragonal with high anisotropy is essential and complex. The samples measured in this paper were annealed in a mixture with fine ground ( 20 m) NaCl. The switching field distributions and activation volumes of two different sizes of particles are presented, 4 and 15 nm. The samples exhibit complex structural behaviour, demonstrating how difficult it is to obtain uniform nanoparticles. We find that the 4-nm particles reverse coherently whereas the 15 nm do not due to inhomogeneous crystallinity.Index Terms-FePt nanoparticle, L1 0 phase, phase transformation.

Annealing Condition Effects on the Structural Properties of FePt Nanoparticles Embedded in MgO via Pulsed Laser Deposition

“…However, a high-temperature post-annealing process will lead to coalescence of NPs and result in magnetic coupling between those ferromagnetic clusters. One way of solving this problem is to embed FePt NPs in a nonmagnetic oxide matrix such as SiO 2 [ 8 , 9 , 10 , 11 ], Al 2 O 3 [ 7 ], MgO [ 12 , 13 ], and NaCl [ 14 , 15 , 16 , 17 ]. Matrix material could offer a homogenous single crystal environment to FePt, and control the orientation of its easily magnetized axis.…”

Colloidal syntheses of FePt nanoparticles

“…There are various techniques for producing colloidal nanoparticles and generally they are classified as either physical or chemical-synthetic methods. Over the past few years, the annealing methods of FePt nanomaterials have gone through tremendous evolution, including for instance the use of a salt matrix [35][36][37][38][39][40], or the use of a doping agent to reduce the annealing temperature [41][42][43][44][45][46]. However, chemical routes often provide a better control over the particle size, shape, composition and crystallinity; all of which in return impact on researchers abilities to tune the nP properties.…”