Frequency-dependent magnetic permeability of Fe10Co90 nanocomposites

The frequency-and temperature-dependent magnetic permeability of a compacted Fe10Co90 nanocomposite was measured over a range of temperatures (77-873 K) and frequencies (0.1-100 kHz). The real and imaginary parts of the complex permeability spectrum showed asymmetries consistent with a distribution of energy barriers and high damping. When the complex permeabilities are scaled relative to the peak frequency of the imaginary permeability, all fall on universal curves. The complex permeability was fitted by modifying the Cole-Davidson model to account for higher damping consistent with predictions for eddy current losses. The physical significance of the relaxation time distribution obtained from the fits is discussed.