Physical interpretation of eddy current losses in ferromagnetic materials. II. Analysis of experimental results

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Abstract
In the preceding paper [J. Appl. Phys. 57, 2110 (1985)], it was shown that the behavior of eddy current losses in ferromagnetic materials can be fully characterized, in general, in terms of two parameters, the effective number ñ0 of active magnetic objects present at low magnetizing frequency fm, and the field V0, determining the ability of the external field to increase the number of active objects with increasing fm. In this paper, the connection of ñ0, V0 with several microstructural and magnetic properties of iron-based ferromagnetic alloys is investigated. It is shown that, in agreement with theoretical predictions, ñ0 is, in general, weakly dependent on other physical properties, attaining values ∼1 in most cases. Only the application of a tensile stress leads to a drastic increase of ñ0 above this limit. V0, on the contrary, turns out to be very sensitive to the type of material. It continuously decreases with decreasing degree of magnetic orientation, changing by about two orders of magnitude when we pass from monocrystalline to nonoriented SiFe alloys. By mapping dynamic losses in the plane (V0, ñ0), it is shown that the loss behavior in the frequency range of applicative interest (fm∼50 Hz) is essentially governed by V0 only, while ñ0 does not play any significant role. The attempt to work out a unified interpretation of the observed properties of V0 leads to a most unexpected direct connection between hysteresis and dynamic losses, which probably underlies some general physical principle, governing the global features of the magnetization dynamics far beyond the details of specific situations.