| Issue |
Europhys. Lett.
Volume 54, Number 4, May 2001
|
|
|---|---|---|
| Page(s) | 526 - 532 | |
| Section | Condensed matter: electronic structure, electrical, magnetic, and optical properties | |
| DOI | https://doi.org/10.1209/epl/i2001-00279-7 | |
| Published online | 01 December 2003 | |
A neutron scattering study of spin precession in ferrimagnetic maghemite nanoparticles
1
Department of Condensed Matter Physics and Chemistry, Risø
National Laboratory DK-4000 Roskilde, Denmark
2
Department of Physics, Building 307, Technical University of
Denmark DK-2800 Kgs. Lyngby, Denmark
Received:
28
August
2000
Accepted:
9
March
2001
We present inelastic neutron scattering studies of 4 nm maghemite nanoparticles. In applied magnetic fields (1-4 T) at 300 K, we observe a clear signal from collective magnetic excitations (spin precession of the whole particle moment). The precession is coherent since it is present at the antiferromagnetic wave vector transfer, 1.31 Å-1. At high fields, the precession frequency varies linearly with field, corresponding to a Landé factor of g = 2.03(2). The intensity of the precession signal varies with temperature (in the range 6-300 K) and applied magnetic field in quantitative agreement with a simple thermodynamic model. The effective anisotropy field is estimated to 0.3(1) T.
PACS: 75.50.Tt – Fine-particle systems; nanocrystalline materials / 76.60.Es – Relaxation effects / 78.70.Nx – Neutron inelastic scattering
© EDP Sciences, 2001
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