ΔE-effect and macroeddy-current damping in nickel

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Abstract
Internal friction measurements on nickel reeds have confirmed the macroeddy‐current limited relaxation behavior predicted by Zener. The macroeddy‐current peak has been observed as a function of frequency, and shown to depend in height and position on the magnetization of the sample. At low frequencies the modulus defect associated with this relaxation causes the ΔE‐effect to exhibit a maximum value at an intermediate magnetization in the vicinity of half the saturation value. As the frequency is raised the maximum disappears and the behavior of the ΔE‐effect reverts to that observed in resonant‐rod experiments. It is emphasized that in this regime, which has frequently been used in the past, the measured ΔE‐effect does not provide an equilibrium characterization of the material.