A Synthetic Route to Size-Controlled fcc and fct FePt Nanoparticles

Howard, Luciano E. M.; Nguyen, Hoang-Hai; Giblin, Sean; Tanner, B. K.; Terry, Ian; Hughes, and Andrew K.; Evans, John S. O.

doi:10.1021/ja051669e

Cited by 99 publications

(96 citation statements)

References 22 publications

(12 reference statements)

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“…Various methods aimed at avoiding sintering have been reported, such as rapid thermal annealing, [2] in-situ thermal annealing, [3] preannealing of surfactant, [4] inert coatings followed by annealing, [5] epitaxial growth at high temperatures (500°C [6] ) or low temperatures (230°C [7] ), metal additives for the reduction of the ordering temperature, [8] covalent bonding with the substrate, [9] salt matrix annealing, [10] and direct L1 0 production in high boiling point solvents. [11] Another problem associated with annealing is incomplete phase transformation due to the dependence of the transformation temperature on particle size. Several workers have suggested that FePt does not order below a critical size of 3 nm in nanoparticles and 4 nm in granular thin films.…”

Section: Introductionmentioning

confidence: 99%

Structure Optimization of FePt Nanoparticles of Various Sizes for Magnetic Data Storage

Tanase

Zhu

Liu

et al. 2007

Metall Mater Trans A

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Surfactant-coated, fcc disordered FePt nanoparticles of three different sizes between 3 and 7 nm were prepared and washed according to a modified reaction route based on Sun et al. [1] Hexane dispersions of nanoparticles were dried on transmission electron microscopy (TEM) grids, and the resulting monolayers were annealed by a sinter-free procedure at 600°C and at 650°C for 2 hours, respectively, developing the L1 0 phase while preserving their monodispersity. The order parameter of the L1 0 phase was measured using electron diffraction from statistically large ensembles of nanoparticles using an X-ray-like signal collection technique. The order parameter increases with particle size and with the temperature in the range 600°C to 650°C, being close to unity for the 7.2-nm particles annealed at 650°C for 2 hours.

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Section: Introductionmentioning

confidence: 99%

Structure Optimization of FePt Nanoparticles of Various Sizes for Magnetic Data Storage

Tanase

Zhu

Liu

et al. 2007

Metall Mater Trans A

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“…In this method, a 1 : 1 molar ratio of platinum acetylacetonate to Na 2 Fe(CO) 4 , and a surfactant oleylamine are sonicated and then refluxed in tetracosane at 389°C under an inert atmosphere. Magnetic measurements of samples produced directly in solution show a coercivity of 1300 Oe at 290 K and 3100 Oe at 10 K. [53] Monodisperse CoPt 3 nanocrystals are synthesized via simultaneous reduction of platinum acetylacetonate and thermodecomposition of cobalt carbonyl in different coordinating mixtures in the presence of 1-adamantanecarboxylic acid. The average particle size can be varied from 1.5 to 7.2 nm by controlling reaction conditions and types of coordinating mixture.…”

Section: Metalsmentioning

confidence: 99%

Chemical Synthesis of Nanostructured Particles and Films

Shi

Sun

Chow

2007

Nanostructured Materials

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“…Since 2000, great efforts have been made to produce monodisperse fct FePt nanoparticles [2][3][4][5][6][7][8] driven by potential applications of the magnetically anisotropic nanoparticles in high-density recording media and high-performance nanocomposite magnets. Recently, we obtained monodisperse fct FePt nanoparticles with retained size and shape by using salts as the annealing separating media.…”

Section: Introductionmentioning

confidence: 99%

Hard magnetic FePt nanoparticles by salt-matrix annealing

Poudyal

Nandwana

et al. 2006

Journal of Applied Physics

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To transfer face-centered-cubic ͑fcc͒ FePt nanoparticles to the face-centered-tetragonal ͑fct͒ phase with high magnetic anisotropy, heat treatments are necessary. The heat treatments lead to agglomeration and sintering of the nanoparticles. To prevent the particles from sintering, salts as the separating media ͑matrix͒ have been used for annealing the nanoparticles in our experiments. The fcc nanoparticles produced by chemical synthesis were mixed with NaCl powders. The mixture was then annealed in forming gas ͑93% H 2 +7%Ar͒ in different conditions to complete the fcc to fct phase transition. After the annealing, the salt was washed out by water and monodisperse fct FePt nanoparticles were obtained. Detailed studies on the effect of the NaCl-to-FePt weight ratios ͑from 1:1 to 400:1͒ have been performed. It was found that a suitable NaCl-to-FePt ratio is the key to obtain monodisperse fct FePt nanoparticles. A higher NaCl-to-FePt ratio is needed for larger particles when the annealing conditions are the same. Increased annealing temperature and time should be accompanied by a higher NaCl-to-FePt ratio. Magnetic measurements show very high coercivity ͑up to 30 kOe͒ of the monodispersed fct nanoparticles by the salt-matrix annealing. 1 The chemically synthesized FePt nanoparticles, however, are of face-centered-cubic ͑fcc͒ phase without magnetic anisotropy. To transfer FePt nanoparticles from fcc phase to face-centered-tetragonal ͑fct͒ phase, heat treatments above 600°C are necessary, which undesirably lead to sintering of these nanoparticles.Since 2000, great efforts have been made to produce monodisperse fct FePt nanoparticles 2-8 driven by potential applications of the magnetically anisotropic nanoparticles in high-density recording media and high-performance nanocomposite magnets. Recently, we obtained monodisperse fct FePt nanoparticles with retained size and shape by using salts as the annealing separating media. 9 The salts can be completely removed after the annealing just by washing the samples in water. High coercivity up to 30 kOe of the fct particles has been obtained. In this paper we report detailed results in controlling the particle morphology and properties by adjusting the salt-to-FePt particle ratio. EXPERIMENTThe fcc FePt nanoparticles with size of 4, 8, and 15 nm were synthesized by chemical solution methods.1,10-13 Sodium chloride ͑NaCl͒ was selected as a separating media in this investigation due to its chemical stability and high solubility in water. NaCl was first ball milled for 24 h to reduce the particle size. The ball-milled NaCl powder was then dispersed in hexane and mixed with hexane dispersion of assynthesized fcc FePt nanoparticles. The mixture was stirred until all the solvent evaporates. Then the mixture was annealed in forming gas ͑93% H 2 +7%Ar͒ in different conditions to complete the fcc to fct transition. The annealed powders were washed in de-ionized water and centrifuged for several times to remove all the NaCl.9 Different NaCl-toFePt weight ratios from 1:1 to 400:1 were t...

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A Synthetic Route to Size-Controlled fcc and fct FePt Nanoparticles

Cited by 99 publications

References 22 publications

Structure Optimization of FePt Nanoparticles of Various Sizes for Magnetic Data Storage

Structure Optimization of FePt Nanoparticles of Various Sizes for Magnetic Data Storage

Chemical Synthesis of Nanostructured Particles and Films

Hard magnetic FePt nanoparticles by salt-matrix annealing

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