Hysteresis and Avalanches

Abstract: In this thesis crackling systems have been investigated. Applying an external force on these systems they respond with events of all sizes. The size distribution follows a power law of the form S¯ . Dierent types appear in nature like avalanches or earthquakes. A magnet exposed to an external magnetic eld will "crackle" as well during its magnetization. Applying the Ising model on the system, a C++ code has been developed to simulate this process. The resulting data has been used to discuss the system with concepts of statistical mechanics like universality or scale invariance. Varying the level of impurity of the magnet, the disorder R, the system exhibits a continuous nonequilibrium phase transition. At its critical point RC the described power law behavior occurs. The critical exponent has been extracted fitting the histogram data with a power law curve. RC has been determined using the behavior of a scaling function for different values of R.