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Title: Experimental evidence for the formation of CoFe{sub 2}C phase with colossal magnetocrystalline-anisotropy

Attainment of magnetic order in nanoparticles at room temperature is an issue of critical importance for many different technologies. For ordinary ferromagnetic materials, a reduction in size leads to decreased magnetic anisotropy and results in superparamagnetic relaxations. If, instead, anisotropy could be enhanced at reduced particle sizes, then it would be possible to attain stable magnetic order at room temperature. Herein, we provide experimental evidence substantiating the synthesis of a cobalt iron carbide phase (CoFe{sub 2}C) of nanoparticles. Structural characterization of the CoFe{sub 2}C carbide phase was performed by transmission electron microscopy, electron diffraction and energy electron spectroscopy. X-ray diffraction was also performed as a complimentary analysis. Magnetic characterization of the carbide phase revealed a blocking temperature, T{sub B}, of 790 K for particles with a domain size as small as 5 ± 1 nm. The particles have magnetocrystalline anisotropy of 4.6 ± 2 × 10{sup 6 }J/m{sup 3}, which is ten times larger than that of Co nanoparticles. Such colossal anisotropy leads to thermally stable long range magnetic order. Moreover, the thermal stability constant is much larger than that of the commonly used FePt nanoparticles. With thermal stability and colossal anisotropy, the CoFe{sub 2}C nanoparticles have huge potential for enhanced magnetic data storage devices.
Authors:
 [1] ;  [2] ; ; ;  [3] ; ;  [1]
  1. Department of Chemistry, Virginia Commonwealth University (VCU), 1001 West Main, Richmond, Virginia 23284 (United States)
  2. (NIS), 136 Tersa, Haram, Giza 12211 (Egypt)
  3. Department of Physics, Virginia Commonwealth University (VCU), 701 West Grace, Richmond, Virginia 23284 (United States)
Publication Date:
OSTI Identifier:
22402505
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 106; Journal Issue: 21; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ANISOTROPY; COBALT; COBALT COMPOUNDS; ELECTRON DIFFRACTION; ELECTRON SPECTROSCOPY; FERROMAGNETIC MATERIALS; IRON CARBIDES; MEMORY DEVICES; NANOPARTICLES; PARTICLE SIZE; SUPERPARAMAGNETISM; TEMPERATURE RANGE 0273-0400 K; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION