| Issue |
Europhys. Lett.
Volume 70, Number 2, April 2005
|
|
|---|---|---|
| Page(s) | 250 - 256 | |
| Section | Condensed matter: electronic structure, electrical, magnetic, and optical properties | |
| DOI | https://doi.org/10.1209/epl/i2004-10485-9 | |
| Published online | 18 March 2005 | |
Magnetic anisotropy and its temperature dependence
in iron-rich 
x
nanoparticles
Fachbereich Physik, Universität Duisburg-Essen Lotharstr. 1, D-47048 Duisburg, Germany
Received:
17
November
2004
Accepted:
2
March
2005
The effective magnetic anisotropy Keff of chemically
disordered 
particles with a mean diameter of
2.3
is shown to be temperature dependent between 50
and 350. From the determination of the blocking
temperatures by field-cooled and zero-field-cooled magnetisation
measurements and ferromagnetic resonance experiments, that is in
two different time windows, we find
at 23.
This is found to be one order of magnitude larger than the bulk
material value for the disordered phase. This value is confirmed
by quantitative simulations of the experimentally determined
zero-field-cooled magnetisation and can be explained by the large
contribution of surface anisotropy, small deviations from a
spherical shape and the presence of an approximately one
monolayer thick iron oxide shell.
PACS: 76.50.+g – Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance / 81.07.Bc – Nanocrystalline materials / 75.30.Gw – Magnetic anisotropy
© EDP Sciences, 2005
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