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Title: Magnetic interactions in γ-Fe{sub 2}O{sub 3}@SiO{sub 2} nanocomposites

Structural and magnetic properties of γ-Fe{sub 2}O{sub 3} nanoparticles of 4 nm diameter, dispersed into silica SiO{sub 2} matrix with a wide range value of volume fraction (0.05 to 1), were investigated. Produced γ-Fe{sub 2}O{sub 3}@SiO{sub 2} nanocomposites consist of an assembly of very small single domain magnetic object (<10 nm) with a random distribution of both inter-particle distance and direction of particle magnetic moment. We focused on the determination of a magnetic percolation threshold, defined as the magnetic particles concentration value above which the magnetic properties of isolated particles vanished in favor of a magnetic collective behavior induced by magnetic interactions. A percolation threshold value of 0.63 was obtained by a local probe technique such as {sup 57}Fe Mössbauer spectrometry and confirmed by global magnetic measurements through zero-field cooled, field-cooled, and ac susceptibility data. Below this threshold, dynamic ac magnetization measurements show a thermally activated Arrhenius dependence of the blocking temperature of superparamagnetic nanoparticles and above this critical value, one observes a slowing down of their dynamic properties, which lead toward the establishment of a spin-glass like state.
Authors:
; ; ;  [1] ; ; ;  [2]
  1. LUNAM Université, Institut des Molécules et Matériaux du Mans, UMR CNRS 6283, Université du Maine Avenue Olivier Messiaen, 72085 Le Mans Cedex 9 (France)
  2. Université de Rennes 1, Institut des Sciences Chimiques de Rennes, UMR UR1-CNRS 6226, Campus de Beaulieu, 35042 Rennes Cedex (France)
Publication Date:
OSTI Identifier:
22314553
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 116; Journal Issue: 5; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CHANNELING; COMPOSITE MATERIALS; FERRITES; INTERACTIONS; IRON 57; IRON OXIDES; MAGNETIC MOMENTS; MAGNETIC PROPERTIES; MAGNETIZATION; NANOPARTICLES; NANOSTRUCTURES; SILICA; SILICON OXIDES; SLOWING-DOWN; SPECTROSCOPY; SPIN GLASS STATE; SUPERPARAMAGNETISM