Hysteresis and avalanches in the site-diluted Ising model: comparison withexperimental results in Cu-Al-Mn alloys

We study the zero temperature properties of hysteresis in a site-diluted Is ing model. The model exhibits a critical line separating a disordered from an incipient ferromagnetic ground state: the shape of the hysteresis loop c hanges from a smooth cycle (formed as a sequence of tiny avalanches) to a s harp cycle exhibiting a macroscopic reversal of the magnetization for a giv en value of the field (infinite avalanche), Criticality is characterized by power-law distribution of avalanche sizes. Model predictions are contraste d with experimental results obtained in Cu-Al-Mn alloys. (C) 2000 Elsevier Science B.V. All rights reserved.