Magnetite nanoparticles about 10 nm sized were synthesized by the polyol method. Zero-field-cooled (ZFC)-FC measurements showed a blocking temperature ∼170 K and the absence of the Verwey transition. They were subsequently consolidated by spark plasma sintering at 750 °C for 15 min, leading to a high density (92% of the theoretical density), solid body, with grains in the 150 nm range. X-ray diffraction patterns exhibited a spinel single phase with cell parameters corresponding to the magnetite structure. Magnetic measurements showed a decrease of coercivity from 685 Oe (54.5 kA/m) at 118 K to 90 Oe (7.2 kA/m) at 139 K. ZFC measurements at 25 Oe presented a three-fold magnetization increase as temperature increased; a small transition between 116 and 117.5 K, followed by a larger one from 117.6 to 124 K. The first transition can be associated with a complex crystallographic transition and delocalization of Fe2+-Fe3+, while the second one can be attributed to spin reorientation due to the magnetocrystalline anisotropy constant (K1) change of sign as previously observed only in magnetite single crystals.
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7 May 2014
PROCEEDINGS OF THE 55TH ANNUAL CONFERENCE ON MAGNETISM AND MAGNETIC MATERIALS
14-18 November 2010
Atlanta, Georgia
Research Article|
Magnetism and Magnetic Materials|
January 27 2014
The Verwey transition in nanostructured magnetite produced by a combination of chimie douce and spark plasma sintering
T. Gaudisson;
T. Gaudisson
1
ITODYS, Université Paris Diderot, PRES Sorbonne Paris Cité, CNRS-UMR 7086
, 75205 Paris Cedex, France
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G. Vázquez-Victorio;
G. Vázquez-Victorio
2
Depto Materiales Metálicos y Cerámicos, Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México
, Mexico 04510, Mexico
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M. Bañobre-López;
M. Bañobre-López
3
International Iberian Nanotechnology Laboratory
, 4715-310 Braga, Portugal
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S. Nowak;
S. Nowak
1
ITODYS, Université Paris Diderot, PRES Sorbonne Paris Cité, CNRS-UMR 7086
, 75205 Paris Cedex, France
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J. Rivas;
J. Rivas
3
International Iberian Nanotechnology Laboratory
, 4715-310 Braga, Portugal
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S. Ammar;
S. Ammar
1
ITODYS, Université Paris Diderot, PRES Sorbonne Paris Cité, CNRS-UMR 7086
, 75205 Paris Cedex, France
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F. Mazaleyrat;
F. Mazaleyrat
4
SATIE, ENS Cachan, CNRS, UniverSud,
F-94230 Cachan, France
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R. Valenzuela
R. Valenzuela
a)
2
Depto Materiales Metálicos y Cerámicos, Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México
, Mexico 04510, Mexico
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a)
Author to whom correspondence should be addressed. Electronic mail: raulvale@yahoo.com.
J. Appl. Phys. 115, 17E117 (2014)
Article history
Received:
September 22 2013
Accepted:
October 28 2013
Citation
T. Gaudisson, G. Vázquez-Victorio, M. Bañobre-López, S. Nowak, J. Rivas, S. Ammar, F. Mazaleyrat, R. Valenzuela; The Verwey transition in nanostructured magnetite produced by a combination of chimie douce and spark plasma sintering. J. Appl. Phys. 7 May 2014; 115 (17): 17E117. https://doi.org/10.1063/1.4863164
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