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

The interplay between material microstructure and magnetic hysteresis is st udied in rapidly quenched Si-Fe alloys. Two ribbons of different average gr ain dimension < s > (35 and 160 mu m) were prepared by annealing at differe nt 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 magnet ization process, the strips were progressively shortened from 30 to 10 cm. The correlation length of a domain-wall jump was estimated through the anal ysis of Barkhausen jump distributions versus apparent permeability. The cor relation length of the coherent magnetization reversals controlling excess dynamic losses was estimated through the Preisach analysis of dynamic hyste resis loops. In the sample with lower < s >, both the Barkhausen and the dy namic loss correlation lengths are comparable to < s >, showing that a sing le structural feature governs all aspects of magnetization reversal. Conver sely, 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].