Studies of high-frequency magnetic permeability of rod-shaped CrO 2 nanoparticles

Abstract

Rod-shaped CrO 2 nanoparticles with an aspect ratio of around 8:1 were studied in this work. The high-frequency properties (complex magnetic permeability, electric permittivity and reflection coefficient) have been measured on a composite consisting of 20 vol% of rod-shaped CrO 2 nanoparticles in a nonmagnetic epoxy resin matrix. The intrinsic magnetic permeability was calculated using an analytical model derived from the Landau-Lifshitz-Gilbert (LLG) equation. The effective permeability of the composite consisting of rod-shaped CrO 2 particles embedded in a nonmagnetic matrix (epoxy resin) was calculated using an effective medium theory for randomly orientated ellipsoidal inclusions. The comparison of the experimental values of the effective permeability with the analytical calculation showed that a relatively good agreement was obtained when the interparticle interactions were taken into the consideration. The results showed that CrO 2 have a natural resonance frequency at around 8 GHz. The microwave absorbing properties of the composite of rod-shaped CrO 2 nanoparticles and epoxy resin were studied. The calculated results of reflection coefficient indicated that the rod-shaped CrO 2 nanoparticles may be interesting for microwave absorption, particularly for the high frequency range around 10 GHz (X-band). © 2007 WILEY-VCH Verlag GmbH & Co. KGaA.