Magnetic Nanocomposites at Microwave Frequencies
Most conventional magnetic materials used in the electronic devices are ferrites, which are composed of micrometer-size grains. But ferrites have small saturation magnetization, therefore the performance at GHz frequencies is rather poor. That is why functionalized nanocomposites comprising magnetic nanoparticles (e.g. composed of Fe, Co) with dimensions ranging from a few nm to 100 nm, and embedded in dielectric matrices (e.g. silicon oxide, aluminium oxide) have a significant potential for the electronics industry. When the size of the nanoparticles is smaller than the critical size for multidomain formation, these nanocomposites can be regarded as an ensemble of particles in single-domain states and the losses (due for example to eddy currents) are expected to be relatively small.
Here we review the theory of magnetism in such materials, and we present a novel measurement method used for the characterization of the electromagnetic properties of composites with nanomagnetic insertions. We also present a few experimental results obtained on composites consisting of iron nanoparticles in a dielectric matrix.
KeywordsDomain Wall Relative Permeability Ferromagnetic Resonance Anisotropy Field Nanoparticle Volume Fraction
This work was supported by the Finnish Funding Agency for Technology and Innovation (TEKES). G.S.P. would like to acknowledge also partial support from the Academy of Finland (Acad. Res. Fellowship 00857 and projects 129896, 118122, and 135135). K.C. wishes to thank the Thailand Commission on Higher Education for financial support.
- 3.R.A. Waldron, Ferrites: An Introduction for Microwave Engineers, (Van Nostrand, London, 1961)Google Scholar
- 4.Super high frequency (2009), http://en.wikipedia.org/wiki/Super_high_frequency
- 7.S. Moerup, M.F. Hansen, Fundamentals and Theory, in Handbook of Magnetism and Advanced Magnetic Materials, ed. by H. Kronmueller, S. Parkin (Wiley, New York, NY, 2007)Google Scholar
- 10.S. Chikazumi, Physics of Ferromagnetism (Oxford University Press, New York, 1997)Google Scholar
- 11.R.C. O’Handley, Modern Magnetic Materials (Wiley, New York, NY, 2000)Google Scholar
- 12.C. Kittel, Introduction to Solid State Physics (Wiley, New York, NY, 1971)Google Scholar
- 13.C.M. Sorensen, Magnetism in Nanoscale Materials in Chemistry, ed. by K.J. Klabunce (Wiley-IEEE, New York, NY, 2001)Google Scholar
- 14.S.J. Steinmuller et al., Effect of substrate roughness on the magnetic properties of thin fcc Co films. Phys. Rev. B 76, (2007)Google Scholar
- 17.L. Landau, E. Lifshitz, On the theory of the dispersion of magnetic permeability in ferromagnetic bodies. Phys. Z. Sowjetunion 8, (1935)Google Scholar
- 18.G.H. Jonker et al., Philips Tech. Rev. 18, 1956 (1956)Google Scholar
- 24.J. Israelachvili, Intermolecular and Surface Forces (Academic, London, 1985)Google Scholar
- 27.Sihvola, Electromagnetic Mixing Formulas and Applications (The Institution of Electrical Engineers, 1999)Google Scholar
- 34.H.P. Klug, L.E. Alexander, X-Ray Diffraction Procedures (Wiley, New York, NY, 1954)Google Scholar
- 35.Å . Björck, Numerical methods for least squares problems, (SIAM, Philadelphia, 1996)Google Scholar