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Magnetization of carbon-coated ferromagnetic nanoclusters determined by electron holography

Published online by Cambridge University Press:  31 January 2011

S. Seraphin ,
C. Beeli ,
J-M. Bonard ,
J. Jiao ,
P. A. Stadelmann  and
A. Châtelain
S. Seraphin*
Affiliation:
Department of Materials Science and Engineering, University of Arizona, Tucson, Arizona 85721
C. Beeli
Affiliation:
Centre Interdépartemental de Microscopie Electronique, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
J-M. Bonard
Affiliation:
Institut de Physique Expérimentale, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
J. Jiao
Affiliation:
Department of Materials Science and Engineering, University of Arizona, Tucson, Arizona 85721
P. A. Stadelmann
Affiliation:
Centre Interdépartemental de Microscopie Electronique, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
A. Châtelain
Affiliation:
Institut de Physique Expérimentale, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
*
a) Address all correspondence to this author. e-mail: seraphin@u.arizona.edu
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Abstract

The magnetic properties of carbon-coated Co and Ni nanoparticles aligned in chains were determined using transmission electron holography. The measurements of the phase change of the electron wave due to the magnetization of the sample were performed. The ratio of remnant magnetization to bulk saturation magnetization Mr/Ms of Co decreased from 53% to 16% and of Ni decreased from 70% to 30% as the particle diameter increased from 25 to 90 nm. It was evident that the inhomogenous magnetic configurations could diminish the stray field of the particles. After being exposed to a 2-Tesla external magnetic field, the Mr/Ms of Co increased by 45% from the original values with the same dependency on the particle size. The Mr/Ms of Ni particles, on the other hand, increased only 10%. The increased magnetization could be attributed to the merging of small domains into larger ones after the exposure to the external magnetic field. The validity of the interpretation of the holograms was established by simulation.

Type
Articles
Information
Journal of Materials Research , Volume 14 , Issue 7 , July 1999 , pp. 2861 - 2870
Copyright
Copyright © Materials Research Society 1999

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