Enhanced magnetic properties of FePt nanoparticles codeposited on Ag nanoislands

Abstract

Ag nanoislands have been used as nucleation sites for FePt nanoparticles when deposited on SiO 2 surfaces by electron beam evaporation. We demonstrate that it is possible to nucleate FePt nanoparticles on predeposited Ag clusters and that this results in a significant improvement of the hard magnetic Ag/FePt nanoparticles' properties. We find that, besides the usual annealing treatments, a simple predeposition of Ag nanoclusters promotes the formation of the FePt L1 0 phase at larger FePt nominal thicknesses ͑f FePt ͒. All the nanoparticles studied are ferromagnetic, except for those FePt samples deposited with lower nominal thicknesses ͑f FePt ϳ 1.8 nm͒, which are superparamagnetic. The presence of Ag seeds promotes the A1 / L1 0 transition, which results in a remarkable enhancement of the coercivity ͑H c ͒ for both the as-deposited and the annealed samples. Maximum H c of 8.9 and 9.4 kOe are obtained for the Ag/FePt nanoparticles with f FePt ϳ 1.8 and 3.5 nm, respectively. Our results are a strong indication that the nucleation of the FePt nanoparticles on Ag nanoclusters can promote significant magnetic hardening of the FePt nanoparticles by easing the transition from the disordered to the ordered phase.

L10-ordered high coercivity (FePt)Ag–C granular thin films for perpendicular recording

“…One of the problems pointed out in these investigations was the need of high temperature annealing ( $ 600 1C) for making the as-sputtered A1 structure ordered to the L1 0 structure [4]. To reduce this kinetic ordering temperature, various additives have been investigated using continuous polycrystalline films [7][8][9][10][11][12][13][14], and Cu and Ag had been found to be effective in reducing the ordering temperature.…”

One-Step Synthesis of High-Coercivity L10-FePtAg Nanoparticles: Effects of Ag on the Morphology and Chemical Ordering of FePt Nanoparticles

“…Similar to gold, Ag atoms are immiscible with both Fe and Pt atoms. Ag has been added to FePt thin films to accelerate the L 1 0 ordering or promote crystallographic orientation. − Ag doped FePt NPs have also been fabricated by chemical or physical methods. − In these synthetic routes, the FePtAg nanoparticles often possess the fcc structure, and a post annealing process is needed. It has been demonstrated that the fcc–fct phase transition temperature for FePt NPs could be reduced by 100–150 °C via doping with silver. , However, reports on the one-step chemical synthesis of fct FePt NPs by using silver as a dopant remain scarce.…”

A perspective on the controlled synthesis of iron-based nanoalloys for the oxygen reduction reaction

“…In general, the fcc FePt can be produced by both physical and chemical methods. The physical vapor deposition (PVD) method has been extensively studied for FePt nano alloyed films with high quality and less defects, 25–29 which can be a good candidate for information storage. However, it usually consumes a long time and calls for precious control.…”