Anomalous eddy current loss and amorphous magnetic materials with low core loss (invited)

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Abstract
Heat‐treatment methods for obtaining low core loss in Fe rich amorphous alloys with high magnetic induction and the physical mechanism concerned will be discussed. Field annealing is necessary to avoid inducing local magnetic anisotropies or magnetic domain wall fixing, and then to make stress relieving effective. Consequently, field annealing can reduce hysteresis energy loss. However, core loss at high frequencies involves a fairly large anomalous eddy current loss. This is due to a large size of 180° magnetic domains resulting from field annealing. Oblique field annealing is, on the other hand, effective to reduce anomalous eddy current loss, because of increase in the number of 180° domain walls. The experimental relation between core loss and domain structure obtained on Fe(72)Co(8)Si(5)B(15) has satisfactorily been explained by the simple model on the basis of bar‐like 180° wall motion. Magnetic properties of Fe(81)‐(B, C, Si) (19) amorphous alloys suitable for transformer materials will also be reported. In Fe(81)B(13)C(2)Si(4), for example, core loss at 50 Hz is 1.3 mw⋅sec/kg at 15 KG and 25°C (2.2 mw⋅sec/kg at 15 KG and 80°C).