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. Averaging over many cycles produces a fingerprint reflecting the reproducibility of the noise. The fingerprint is not strongly temperature or driving-rate dependent, indicating that the variability is a consequence of dynamical effects. We also find that the slope of the cycle-averaged magnetization, $\frac{d〈M〉}{\mathrm{dH}}$, is correlated with the cycle-to-cycle variations in magnetization, $〈{\left(\delta M\right)}^2〉$.