Microwave Frequency-Domain Spectroscopy of Complex Heterogeneous Nanocomposites: The Electromagnetic Functionality

ABSTRACT

We present systematic effective permeability measurements of nanostructured granular systems composed of magnetic (Ni) grains embedded in a nonmagnetic (ZnO) matrix using broadband microwave spectroscopy. Using the transmission/reflection waveguide method, the effective complex permeability was measured in the frequency range 0.01–10 GHz. From the data collected, it is found that a mean-field approach (effective medium approximation) is appropriate for understanding the permeability of composite materials characterized by submicrometer inclusion length scales. A systematic study of the room temperature effective permeability tensor of these composite samples is performed and provides a signature for the nonreciprocity of wave propagation in these nanostructures.

KEYWORDS:

• effective magnetic permeability
• microwave
• nanocomposites

ACKNOWLEDGMENTS

The article is a much belated revision of lecture notes I provided for the Rencontre Internationale de Spectroscopie et d'Optique (RISO 2007) held in June 2007 at Kénitra (Morocco). Many colleagues have helped me to understand the issues covered in this topical review, and I thank particularly S. Mallégol, P. Quéffelec, and J Ben Youssef for many useful discussions and A.-M. Konn, F. Michaud, D. Rozuel, G. Sinquin, and P. Talbot for their technical assistance. The Laboratoire d'Electronique et Systèmes de Télécommunications is Unité Mixte de Recherche CNRS 6165.

Notes

^a From manufacturer product literature.

^b Determined from specific surface area.

^c Checked by transmission electron microscopy images.

^d Checked by X-ray diffraction experiments.

Compaction pressure for all composites was 10⁷ Nm for 2 min.