REPRODUCIBILITY OF MAGNETIC AVALANCHES IN AN FE-NI-CO FERROMAGNET

A study of magnetic avalanches in Perminvar, an Fe-Ni-Co alloy, shows that some avalanches are almost exactly reproducible from one magnetic field cycle to the next, while others show significant variability. A veraging over many cycles produces a fingerprint reflecting the reprod ucibility of the noise. The fingerprint is not strongly temperature or driving-rate dependent, indicating that the variability is a conseque nce of dynamical effects. We also find that the slope of the cycle-ave raged magnetization, d[M]/dH, is correlated with the cycle-to-cycle va riations in magnetization, [(delta M)(2)].