Negative permeability spectra in Permalloy granular composite materials

TLDR: In this article, a negative permeability has been obtained above 5GHz due to the natural magnetic resonance in the 70vol% particle content composite material and the electrical permittivity spectra show a nonmetallic characteristic.

Abstract: Complex permeability spectra of Permalloy granular composite materials have been studied in the microwave frequency range. The heat-treated Permalloy particles in the air at several hundreds of °C have a high surface electrical resistance; the eddy current effect in the high frequency permeability spectra can be suppressed in the composite structure containing the percolated particles. A negative permeability has been obtained above 5GHz due to the natural magnetic resonance in the 70vol% particle content composite material. In this content, electrical permittivity spectra show a nonmetallic characteristic. This permeability dispersion can be applied for the left-handed media.

Figures

FIG. 4. Complex permeability a and permittivity b spectra for the Permalloy composite materials containing heat-treated particles at 300 °C for 5 h.

FIG. 3. Magnetization curves for the Permalloy particles which are nontreated and heat treated at 300, 400, and 600 °C for 5 h.

FIG. 2. The ac electrical resistivity for the Permalloy particles as a function of frequency, which are nontreated and heat treated at 300, 400, and 600 °C for 5 h.

FIG. 1. Powder x-ray diffraction profiles for the Permalloy which are nontreated and heat treated at 300, 400, and 600 °C for 5 h.