Magnetization loss of nanocrystalline soft magnets

FeCuNbSiB-ribbons with optimized nanocrystalline microstructure possess a unique combination of near-zero magnetostriction, high saturation induction and low magnetization losses. Due to the absence of distinct intrinsic anisotropies, the magnetization curve can be adjusted by field-annealing to square or flat shape. It is well known that excess losses are an important loss component of soft magnets with square hysteresis loop. Yet, even cores of flat type loop can show significant excess losses. The paper reviews the loss mechanisms for excess losses in nanocrystalline soft magnets on the basis of Kerr-microscopy observation and loss theory and compares it to amorphous materials.