Low power loss in Fe65.5Cr4Mo4Ga4P12B5.5C5 bulk metallic glasses

• We study the frequency dependent power losses of bulk Fe-based glasses.
• We study the induction dependent power losses of bulk Fe-based glasses.
• We study the thickness dependent power losses of bulk Fe-based glasses.
• Low total power loss in bulk glasses is caused by low excess eddy current loss.
• Anneal largely decreases the total power loss of bulk Fe-based glasses.

Power loss – one of the important application-oriented magnetic properties of ferromagnetic metallic glasses – has been well studied in glassy ribbons rather than bulk metallic glasses. This paper studies the influence of frequency, induction, annealing, and specimen thickness on the total power loss – which is divided into hysteresis loss, classical eddy current loss, and excess eddy current loss – of bulk ferromagnetic Fe65.5Cr4Mo4Ga4P12B5.5C5 glasses. The total power loss of bulk glasses increases with frequency and peak induction and follows a power relation, similar to what has been observed in glassy ribbons. Annealing decreases both the hysteresis loss and the classical eddy current loss, resulting in a lower total power loss. The ratio of excess eddy current loss to classical eddy current loss deceases with increasing specimen thickness. The excess eddy current loss is negligible for our thickest glass and comparable to the classical eddy current loss for our thinner glasses. In contrast, the excess eddy current loss is often at least one to two orders of magnitude greater than the classical eddy current loss in glassy ribbons. The low total power loss achieved in bulk ferromagnetic glasses should be beneficial to their practical applications in energy conversion devices.

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