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Title: Spin orientation, structure, morphology, and magnetic properties of hematite nanoparticles

Monodisperse hematite (α-Fe{sub 2}O{sub 3}) nanoparticles were synthesized by forced hydrolysis of acidic Fe{sup 3+} solution. Rietveld analysis was applied to the X-ray powder diffraction data to refine the lattice constants and atomic positions. The lattice constants for a hexagonal unit cell were determined to be a ∼ 0.50327 and c ∼ 1.37521 nm. High resolution transmission electron microscopy was employed to study the morphology of the particles. Atomic scale micrographs and diffraction patterns from several zone axes were obtained. These reveal the high degree of crystallinity of the particles. A series of observations made on the particles by tilting them through a range of ±45° revealed the particles to be micaceous with stacking of platelets with well defined crystallographic orientations. The Morin transition in these nanoparticles was found to occur at 210 K, which is lower temperature than 263 K of bulk hematite. It was ascertained from the previous Mössbauer studies that the spin orientation for nano-sized hematite particle flips from 90° to 28° with respect to the c-axis of the hexagonal structure during the Morin transition, which is in contrast to that observed in bulk hematite where spin orientation flips from 90° to 0°.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Western Digital Corporation, San Jose, California 95138 (United States)
  2. Intel Corporation, Chandler, Arizona 85226 (United States)
  3. Seagate Technology, Bloomington, Minnesota 55435 (United States)
  4. Department of Electrical and Computer Engineering, University of Alabama, Tuscaloosa, Alabama 35487 (United States)
  5. Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States)
Publication Date:
OSTI Identifier:
22403022
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 17; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; CRYSTAL STRUCTURE; FERRITES; HEMATITE; IRON IONS; IRON OXIDES; LATTICE PARAMETERS; MAGNETIC PROPERTIES; MORPHOLOGY; NANOPARTICLES; NANOSTRUCTURES; SPIN ORIENTATION; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION