Surface effects on the magnetic properties of ultrafine cobalt particles

M. Respaud, J. Broto, H. Rakoto, A. R. Fert, L. Thomas, B. Barbara, M. Verelst, E. Snoeck, P. Lecante, A. Mosset, J. Osuna, Mohamed Teyeb Ould Ely, C. Amiens, B. Chaudret

Research output: Contribution to journalArticle

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Abstract

Monodispersed nanoparticles of cobalt have been prepared by an original method using the decomposition under hydrogen of an organometallic precursor in the presence of a stabilizing polymer. Two colloids (Coll-I and Coll-II) have been obtained by changing the organometallic concentration in the polymer. Observation by high-resolution transmission electronic microscopy (HRTEM) showed Co particles well isolated and regularly dispersed in the polymer with a very narrow size distribution centered around 1.5 nm (Coll-I) and 2 nm (Coll-II) diameter. These particles are superparamagnetic above the blocking temperature 9 K (Coll-I) and 13.5 K (Coll-II). The particle size deduced from the analyses of the magnetic susceptibilities and magnetization curves are consistent with those measured by HRTEM. Magnetization at 5 K seems to saturate in fields up to 5 T leading to an enhanced mean magnetic moment per atom for both samples, where (Formula presented) for the smallest particles. High-field magnetization measurements, up to 35 T, increases nearly linearly with the applied field. This is equivalent to an increase of the mean magnetic moment with (Formula presented) at 35 T for the smallest particles. The effective magnetic anisotropies are found to be larger than that of the bulk materials and decrease with increasing particle size. This set of data allows us to conclude that the enhanced magnetization, its increase with applied magnetic field, and the enhanced effective magnetic anisotropy are associated with the large influence of the surface atoms and are more significant with decreasing size.

Original languageEnglish
Pages (from-to)2925-2935
Number of pages11
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume57
Issue number5
DOIs
Publication statusPublished - Jan 1 1998
Externally publishedYes

Fingerprint

Cobalt
Magnetization
Magnetic properties
cobalt
magnetic properties
Polymers
Magnetic anisotropy
Organometallics
Magnetic moments
magnetization
Microscopic examination
Particle size
Atoms
polymers
Colloids
magnetic moments
Magnetic susceptibility
microscopy
Hydrogen
anisotropy

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

Cite this

Respaud, M., Broto, J., Rakoto, H., Fert, A. R., Thomas, L., Barbara, B., ... Chaudret, B. (1998). Surface effects on the magnetic properties of ultrafine cobalt particles. Physical Review B - Condensed Matter and Materials Physics, 57(5), 2925-2935. https://doi.org/10.1103/PhysRevB.57.2925

Surface effects on the magnetic properties of ultrafine cobalt particles. / Respaud, M.; Broto, J.; Rakoto, H.; Fert, A. R.; Thomas, L.; Barbara, B.; Verelst, M.; Snoeck, E.; Lecante, P.; Mosset, A.; Osuna, J.; Teyeb Ould Ely, Mohamed; Amiens, C.; Chaudret, B.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 57, No. 5, 01.01.1998, p. 2925-2935.

Research output: Contribution to journalArticle

Respaud, M, Broto, J, Rakoto, H, Fert, AR, Thomas, L, Barbara, B, Verelst, M, Snoeck, E, Lecante, P, Mosset, A, Osuna, J, Teyeb Ould Ely, M, Amiens, C & Chaudret, B 1998, 'Surface effects on the magnetic properties of ultrafine cobalt particles', Physical Review B - Condensed Matter and Materials Physics, vol. 57, no. 5, pp. 2925-2935. https://doi.org/10.1103/PhysRevB.57.2925
Respaud, M. ; Broto, J. ; Rakoto, H. ; Fert, A. R. ; Thomas, L. ; Barbara, B. ; Verelst, M. ; Snoeck, E. ; Lecante, P. ; Mosset, A. ; Osuna, J. ; Teyeb Ould Ely, Mohamed ; Amiens, C. ; Chaudret, B. / Surface effects on the magnetic properties of ultrafine cobalt particles. In: Physical Review B - Condensed Matter and Materials Physics. 1998 ; Vol. 57, No. 5. pp. 2925-2935.
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AU - Barbara, B.

AU - Verelst, M.

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AU - Lecante, P.

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