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Title: Direct Synthesis and Size Selection of Ferromagnetic FePt Nanoparticles

Abstract

A one-step synthesis of L10 FePt nanoparticles ca. 17.0 nm in diameter by reductive decomposition of the single-source precursor, FePt(CO)4dppmBr2, on a water-soluble support (Na2CO3) is demonstrated. Direct conversion of a FePt(CO)4dppmBr2/Na2CO3 composite to a L10 FePt/Na2CO3 nanocomposite occurs at 600 C under getter gas with metal-ion reduction and minimal nanoparticle coalescence. Triturating the resulting nanocomposite with water simultaneously dissolves the sodium carbonate solid support and precipitates the formed fct FePt nanoparticles. As-prepared FePt nanoparticles are ferromagnetic and exhibit coercivities of 14.5 kOe at 300 K and 21.8 kOe at 5 K. When capped by functionalized methoxypoly(ethylene glycol) surfactant molecules, as-prepared, polydisperse ferromagnetic FePt nanoparticles can be dispersed and size-selected by fractional precipitation.

Authors:
 [1];  [1];  [2];  [2];  [2];  [1];  [1]
  1. Vanderbilt University
  2. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Shared Research Equipment Collaborative Research Center
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
931894
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Chemistry of Materials; Journal Volume: 19; Journal Issue: 10
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 77 NANOSCIENCE AND NANOTECHNOLOGY; IRON ALLOYS; PLATINUM ALLOYS; FERROMAGNETIC MATERIALS; PARTICLE SIZE; SYNTHESIS; NANOSTRUCTURES; PRECURSOR; COERCIVE FORCE; FePt; ferromagnetism; L10 ordering; TEM; nanoparticles; synthesis; size selection

Citation Formats

Wellons, M.S., MorrisIII, William H, Gai, Zheng, Shen, Jian, Bentley, James, Wittig, J. E., and Lukehart, C.M. Direct Synthesis and Size Selection of Ferromagnetic FePt Nanoparticles. United States: N. p., 2007. Web. doi:10.1021/cm062455e.
Wellons, M.S., MorrisIII, William H, Gai, Zheng, Shen, Jian, Bentley, James, Wittig, J. E., & Lukehart, C.M. Direct Synthesis and Size Selection of Ferromagnetic FePt Nanoparticles. United States. doi:10.1021/cm062455e.
Wellons, M.S., MorrisIII, William H, Gai, Zheng, Shen, Jian, Bentley, James, Wittig, J. E., and Lukehart, C.M. Mon . "Direct Synthesis and Size Selection of Ferromagnetic FePt Nanoparticles". United States. doi:10.1021/cm062455e.
@article{osti_931894,
title = {Direct Synthesis and Size Selection of Ferromagnetic FePt Nanoparticles},
author = {Wellons, M.S. and MorrisIII, William H and Gai, Zheng and Shen, Jian and Bentley, James and Wittig, J. E. and Lukehart, C.M.},
abstractNote = {A one-step synthesis of L10 FePt nanoparticles ca. 17.0 nm in diameter by reductive decomposition of the single-source precursor, FePt(CO)4dppmBr2, on a water-soluble support (Na2CO3) is demonstrated. Direct conversion of a FePt(CO)4dppmBr2/Na2CO3 composite to a L10 FePt/Na2CO3 nanocomposite occurs at 600 C under getter gas with metal-ion reduction and minimal nanoparticle coalescence. Triturating the resulting nanocomposite with water simultaneously dissolves the sodium carbonate solid support and precipitates the formed fct FePt nanoparticles. As-prepared FePt nanoparticles are ferromagnetic and exhibit coercivities of 14.5 kOe at 300 K and 21.8 kOe at 5 K. When capped by functionalized methoxypoly(ethylene glycol) surfactant molecules, as-prepared, polydisperse ferromagnetic FePt nanoparticles can be dispersed and size-selected by fractional precipitation.},
doi = {10.1021/cm062455e},
journal = {Chemistry of Materials},
number = 10,
volume = 19,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Ferromagnetic SmCo{sub 5} nanoparticles with large size have been directly synthesized by a magnetron-sputtering-based gas-phase condensation method. Based on this method, we studied the effect of thermodynamic environment for the growth of SmCo{sub 5} nanoparticles. It was found that the well-crystallized SmCo{sub 5} nanoparticle tends to form a hexagonal disk shape with its easy axis perpendicular to the disk plane. More importantly, under the condition of high sputtering current, well-crystallized nanoparticles were found to be formed through a three-stage growth process: aggregation, coalescence, and second crystallization.
  • Partially ordered Fe{sub 53}Pt{sub 47} nanoparticles with size around 8 nm were prepared by the simultaneous decomposition of iron pentacarbonyl and platinum acetylacetonate. The high boiling point chemical, hexadecylamine, was used as a solvent, and 1-adamantanecarboxylic acid was used as a stabilizer. The reflux temperature of the solution could exceed 360 deg. C, where disordered FePt particles could be partially transformed into the ordered L1{sub 0} phase. A nonmagnetic mechanical stirrer was used in order to avoid agglomeration of the fct-FePt particles during synthesis. The particles were dispersed in toluene and films of the particles were cast onto silicon wafersmore » from the solution. X-ray diffraction patterns of as-made samples showed weak superlattice peaks, indicating partial chemical ordering of the Fe{sub 53}Pt{sub 47} particles. The room-temperature hysteresis loop of the as-made sample reveals a small coercivity ({approx}600 Oe) because of thermal fluctuations; however, the loop is wide open and hard to saturate. The remanence coercivity from the dcd curve is about 2.5 kOe, which is four times larger than the hysteresis coercivity. The large remanent to hysteresis coercivity ratio and the shapes of the hysteresis loop and dcd curve suggest a broad distribution of anisotropies in the partially ordered particles. By coating the ordered nanoparticles with a polymer binder, the easy axis of the particles could be aligned under an external field.« less
  • No abstract prepared.
  • No abstract prepared.
  • The kinetics of order-disorder transition of FePt nanoparticles during high temperature annealing is theoretically investigated. A model is developed to address the influence of large surface to volume ratio of nanoparticles on both the thermodynamic and kinetic aspect of the ordering process; specifically, the nucleation and growth of L1{sub 0} ordered domain within disordered nanoparticles. The size- and shape-dependence of transition kinetics are quantitatively addressed by a revised Johnson-Mehl-Avrami equation that included corrections for deviations caused by the domination of surface nucleation in nanoscale systems and the non-negligible size of the ordered nuclei. Calculation results based on the model suggestedmore » that smaller nanoparticles are kinetically more active but thermodynamically less transformable. The major obstacle in obtaining completely ordered nanoparticles is the elimination of antiphase boundaries. The results also quantitatively confirmed the existence of a size-limit in ordering, beyond which, inducing order-disorder transitions through annealing is impossible. A good agreement is observed between theory, experiment, and computer simulation results.« less