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Title: Formation of FePt Nanoparticles Having High Coercivity

Abstract

Ultrasonication of toluene solutions of the heteropolynuclear cluster complex, Pt{sub 3}Fe{sub 3}(CO){sub 15}, in the presence of oleic acid and oleylamine affords surface-capped fcc FePt nanoparticles having an average diameter of ca. 2 nm. Self-assembled arrays of these nanoparticles on oxidized Si wafers undergo a fcc-to-fct phase transition at 775 C to form ferromagnetic FePt nanocrystals ca. 5.8 nm in diameter well dispersed on the Si wafer surface. Room-temperature coercivity measurements of these annealed FePt nanoparticles confirm a high coercivity of ca. 22.3 kOe. Such high coercivity for fct FePt nanoparticles might result from use of a heterpolynuclear complex as a single-source precursor of Fe and Pt neutral atoms or from use of ultrasonication to form fcc FePt nanoparticles under conditions of exceptionally rapid heating. Experiments to determine the critical experimental conditions required to achieve such high room-temperature coercivities in ferromagnetic nanoparticles are underway.

Authors:
 [1];  [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:
931893
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the American Chemical Society; Journal Volume: 128; Journal Issue: 44
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 77 NANOSCIENCE AND NANOTECHNOLOGY; SYNTHESIS; IRON ALLOYS; PLATINUM ALLOYS; NANOSTRUCTURES; CRYSTAL-PHASE TRANSFORMATIONS; COERCIVE FORCE; FePt; ferromagnetism; L10 ordering; TEM; nanoparticles; coercivity

Citation Formats

Rutledge, R.D., MorrisIII, William H, Wellons, M.S., Gai, Zheng, Shen, Jian, Bentley, James, Wittig, J. E., and Lukehart, C.M.. Formation of FePt Nanoparticles Having High Coercivity. United States: N. p., 2006. Web. doi:10.1021/ja0633868.
Rutledge, R.D., MorrisIII, William H, Wellons, M.S., Gai, Zheng, Shen, Jian, Bentley, James, Wittig, J. E., & Lukehart, C.M.. Formation of FePt Nanoparticles Having High Coercivity. United States. doi:10.1021/ja0633868.
Rutledge, R.D., MorrisIII, William H, Wellons, M.S., Gai, Zheng, Shen, Jian, Bentley, James, Wittig, J. E., and Lukehart, C.M.. Sun . "Formation of FePt Nanoparticles Having High Coercivity". United States. doi:10.1021/ja0633868.
@article{osti_931893,
title = {Formation of FePt Nanoparticles Having High Coercivity},
author = {Rutledge, R.D. and MorrisIII, William H and Wellons, M.S. and Gai, Zheng and Shen, Jian and Bentley, James and Wittig, J. E. and Lukehart, C.M.},
abstractNote = {Ultrasonication of toluene solutions of the heteropolynuclear cluster complex, Pt{sub 3}Fe{sub 3}(CO){sub 15}, in the presence of oleic acid and oleylamine affords surface-capped fcc FePt nanoparticles having an average diameter of ca. 2 nm. Self-assembled arrays of these nanoparticles on oxidized Si wafers undergo a fcc-to-fct phase transition at 775 C to form ferromagnetic FePt nanocrystals ca. 5.8 nm in diameter well dispersed on the Si wafer surface. Room-temperature coercivity measurements of these annealed FePt nanoparticles confirm a high coercivity of ca. 22.3 kOe. Such high coercivity for fct FePt nanoparticles might result from use of a heterpolynuclear complex as a single-source precursor of Fe and Pt neutral atoms or from use of ultrasonication to form fcc FePt nanoparticles under conditions of exceptionally rapid heating. Experiments to determine the critical experimental conditions required to achieve such high room-temperature coercivities in ferromagnetic nanoparticles are underway.},
doi = {10.1021/ja0633868},
journal = {Journal of the American Chemical Society},
number = 44,
volume = 128,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • No abstract prepared.
  • No abstract prepared.
  • The microstructure and the room-temperature hysteretic magnetic properties of sputtered, 10 nm thin films of equiatomic binary alloys of CoPt and FePt were characterized using transmission electron microscopy (TEM) and a superconducting quantum interference device (SQUID) magnetometer. A transformation from an atomically disordered, face-centered-cubic structure to the L1{sub 0} ordered structure occurred during postdeposition annealing and was characterized using digital analysis of dark-field TEM images. The transformation was observed to follow first-order nucleation and growth kinetics, and the ordered volume fraction transformed was quantified at numerous points during the transformation. The ordered volume fraction was then compared to the magneticmore » coercivity data obtained from the SQUID magnetometer. In contrast to the relationship most commonly described in the literature, that the highest coercivity corresponds to a two phase ordered/disordered mixture, the maximum value for coercivity in this study was found to correspond to the fully ordered state. Furthermore, in samples that were less than fully ordered, a direct relationship between ordered volume fraction and coercivity was observed for both CoPt and FePt. The proposed mechanism for the high coercivity in these films is an increasing density of magnetic domain wall pinning sites concurrent with an increasing fraction of ordered phase. {copyright} {ital 1999 American Institute of Physics.} thinsp« less
  • The alloy Fe{sub 35}Pt{sub 35}P{sub 30}, whose composition is close to a ternary eutectic, was rapidly solidified by melt spinning and the ribbon exhibited a high coercivity, exceeding 20 kOe after annealing. The alloy was mainly composed of L1{sub 0} ordered FePt and PtP{sub 2} with an average grain size of about 50 nm. In the as-cast state, the alloy was comprised of about 20-nm-diam FePt and PtP{sub 2} grains supersaturated with P and Fe, respectively, and the coercivity was only 150 Oe. The high coercivity obtained following annealing is discussed on the basis of the microstructural observations.
  • FePt-C films with high coercivity (001) texture, and small grain size were deposited on MgO/CrRu/glass substrate by cosputtering FePt and carbon at 350 deg. C. The out-of-plane coercivity measured at room temperature increased from 9.6 to 15.1 kOe when C concentrations increased from 0% to 15%. Further increasing the C contents to 20% and 25% caused the decrease of coercivity to 13.6 and 11.8 kOe, respectively. With C doping, a two-layer structure of FePt-C films was formed and fcc-phase FePt particles were found. By optimizing the sputtering process, FePt-C (001) film with coercivity higher than 14.4 kOe and columnar FePtmore » grains of 7.5 nm in diameter was obtained, which are suitable for ultrahigh density perpendicular recording.« less