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Journal of Nanomaterials
Volume 2007, Article ID 27437, 16 pages
http://dx.doi.org/10.1155/2007/27437
Research Article

Broadband Ferromagnetic Resonance Measurements in Ni/ZnO and Niγ-Fe2O3 Nanocomposites

1Laboratoire d'Electronique et Systèmes de Télécommunications (UMR CNRS 6165), Université de Bretagne Occidentale, CS 93837, 6 avenue Le Gorgeu, Brest Cedex 3 29238, France
2Laboratoire de Magnétisme de Bretagne (FRE CNRS 2697), Université de Bretagne Occidentale, CS 93837, 6 avenue Le Gorgeu, Brest Cedex 3 29238, France
3Département de Physique, Université de Bretagne Occidentale, CS 93837, 6 avenue Le Gorgeu, Brest Cedex 3 29238, France

Received 16 February 2007; Accepted 27 June 2007

Academic Editor: Donald A. Bansleben

Copyright © 2007 Vincent Castel et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

A comparative study at the ambient temperature of the ferromagnetic resonance (FMR) spectra of Ni/ZnO and Ni/γ-Fe2O3 nanocomposites (NCs) is reported. A microstrip transmission line technique was used to measure the FMR profiles and linewidths in the 8–24 GHz frequency range. The samples were placed at the center of a microstrip line where the derivative of the absorbed power was measured using a standard ac field modulation technique (10 Oe amplitude) and lock-in detection. The analysis of the FMR spectra can be interpreted as arising from aggregates of magnetic nanoparticles, each of which resonates in an effective magnetic field composed of the applied field, the average (magnetostatic) dipolar field, and the randomly oriented magnetic anisotropy field. It is found that frequency and applied magnetic field strongly influence the lineshape of the FMR spectra. Two observations are identified within the FMR spectra. On the one hand, the resonance field increased linearly with frequency as expected from uniform mode theory and yielded a Landé g factor in the range 1.48–2.05. On the other hand, there is no clear correlation between FMR linewidths and frequency. Inhomogeneity-based line-broadening mechanisms, due to the damping of surface/interface effects and interparticle interaction, affect the FMR effective linewidth.