High frequency microwave absorbing properties of cobalt nanowires with transverse magnetocrystalline anisotropy

Cobalt nanowires with transverse magnetocrystallme anisotropy have been fabricated and the dynamic permittivity and permeability spectra of the nanowire/paraffin composite were measured in the frequency range of 0.5-18 GHz. The imaginary part of the permeability spectra for the nanowire/paraffin composite samples exhibits a strong absorption peak at 6 1 GHz and two minor peaks at above 10 GHz. It is determined that the peak at 6.1 GHz is attributed to the natural resonance mechanism and the other two peaks are caused by eddy current effect. The permeability spectra attributed to natural resonance are fitted using the LLG equation and further confirmed by calculation based on the Kittel formula. The electromagnetic wave reflection loss values of the nanowire/paraffin composite sample are lower than -20 dB when the thickness of the nanowire/paraffin composite is adjusted, suggesting that the cobalt nanowire composites are promising candidates as microwave absorbers. (C) 2009 Elsevier B.V. All rights reserved.