Enhanced Chemical Ordering and Coercivity in FePt Alloy Nanoparticles by Sb‐Doping

Abstract

Sb doping stabilizes the chemically ordered tetragonal L10 structure in FePt alloy nanoparticles, yielding higher coercivities (Hc) at lower annealing temperatures (see Figure) than previously reported. Upon annealing to ∼ 300 °C, nanoparticles yield coercivities more than ten times those previously reported for FePt nanoparticles of similar sizes annealed to the same temperature. These findings are of importance for ultrahigh‐density memory device applications.

Recent Advances in Chemical Synthesis, Self‐Assembly, and Applications of FePt Nanoparticles

“…[104] The same strategy can be applied to chemically made monodisperse FePt nanoparticles. Several classes of monodisperse ternary nanoparticles of FePtCu, [105] FePtAg, [106] FePtAu, [107,108] and FePtSb [109] have been successfully synthesized by a thermal decomposition and reduction method. The fcc to fct structure transformation temperature can be decreased to as low as 300°C.…”

High thermal stability of carbon-coated L10-FePt nanoparticles prepared by salt-matrix annealing

“…Though dopants have been used to reduce the phase transition temperature, they also result in enhanced grain growth. [6][7][8] Direct chemical synthesis of L1 0 -FePt nanoparticles has also been explored but only limited magnetic hardening was acheived. 9,10 Alternatively, SiO 2 coating of FePt particles has been used to prevent particle sintering during the high-temperature magnetic hardening process.…”

High-Coercivity FePt Nanoparticle Assemblies Embedded in Oxide-Matrix by Atomic Layer Deposition

“…When the thickness of the Al 2 O 3 capping layer increases to 15 and 20 nm, the average particle sizes keep almost constant in FePt/Al 2 O 3 composite lms. In addition, with the increase of the capping layer, the long-range S values [6] decrease, which is attributed to the smaller FePt particles embedded in the Al 2 O 3 -matrix (the particle size eect [13]) and the residual strain at the interfaces. The excessive matrix layer would hinder the L1 0 phase transition [10] and decrease the ordering parameter.…”

“…• C by doping Sb, and the ordering is promoted by defects produced by the additives during annealing, because those additives with very low surface energy are easy to segregate, resulting in the diculty in formation of large-area assembly [6,7]. In order to overcome above problems, FePt NPs are either annealed by a salt-matrix technique [8], or coated with SiO 2 [9] or MgO [10] to minimize the sintering eects during the L1 0 -phase transition annealing.…”