Interface depinning, self-organized criticality, and the Barkhausen effect.

Abstract

We report measurements of magnetic avalanches in a Fe-Ni-Co alloy. The distribution of avalanche sizes is given by $P(A)\ensuremath{\propto}{A}^{\ensuremath{-}\ensuremath{\alpha}}\mathrm{exp}({\ensuremath{-}A/A}_{0})$, with $\ensuremath{\alpha}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.33\ifmmode\pm\else\textpm\fi{}0.10$. The role of demagnetizing effects in the avalanche statistics is demonstrated. We analyze a simple model of interface growth and find a power law distribution of avalanche sizes over a wide range of parameters when an infinite-range demagnetization field is included. The exponents agree with those found at the critical field in the absence of demagnetization effects.