Connection between hysteresis, Barkhausen noise, and microstructure in magnetic materials

The interplay between material microstructure and magnetic hysteresis is studied in rapidly quenched Si-Fe alloys. Two ribbons of different average grain dimension < s > (35 and 160 mu m) were prepared by annealing at different temperatures and studied through two independent approaches: Barkhausen noise measurements, and Preisach analysis of static and dynamic hysteresis loops. In order to monitor the effect of demagnetizing fields on the magnetization process, the strips were progressively shortened from 30 to 10 cm. The correlation length of a domain-wall jump was estimated through the analysis of Barkhausen jump distributions versus apparent permeability. The correlation length of the coherent magnetization reversals controlling excess dynamic losses was estimated through the Preisach analysis of dynamic hysteresis loops. In the sample with lower < s >, both the Barkhausen and the dynamic loss correlation lengths are comparable to < s >, showing that a single structural feature governs all aspects of magnetization reversal. Conversely, in the high < s > sample, the ribbon thickness competes with < s > in controlling static and dynamic magnetization processes. (C) 2000 American Institute of Physics. [S0021-8979(00)77808-X].