Mechanism of subcritical avalanche propagation in three-dimensional disordered systems

Hysteresis-loop phenomena in disordered ferromagnets with demagnetizing field and finite temperature

Using numerical simulations, we investigate the impact of the demagnetization field and finite temperature on the hysteresis phenomena in disordered ferromagnetics systems. We model the behavior of thin systems employing the thermal nonequilibrium random field Ising model driven by a finite-driving rate protocol to study the shape of the hysteresis loop and demagnetization line and the magnetization fluctuations for varied parameters. Our results reveal a significant interplay of the disorder, the demagnetizing fields, and thermal fluctuations. In particular, at a fixed disorder and temperature, the increasing demagnetization coefficient gradually prologues the magnetization reversal process, altering the multifractal nature of the magnetization fluctuations. The process accompanies the appearance of extended linear segments in the hysteresis loop and changes in the demagnetization line while practically preserving the value of the coercive field and slightly changing the remanent magnetization. On the other hand, increasing temperature expands the system's response fluctuations and narrows the loop, affecting the coercive field and remanent magnetization. The interplay of thermal fluctuations and demagnetizing fields fully manifests in limiting the large-scale magnetization fluctuations, revealed by the multifractal spectra and the scaling functions of the avalanches. Our research offers new modeling perspectives with a more realistic scenario and provides insight into new hysteresis loop phenomena relevant to theoretical analysis and applications.

Interplay of disorder and type of driving in disordered ferromagnetic systems

We investigate the effects of adiabatic, quasistatic, and finite-rate types of driving on the evolution of disordered three-dimensional ferromagnetic systems, studied within the frame of the nonequilibrium athermal random field Ising model. The effects were examined in all three domains of disorder (low, high, and transitional) for all types of driving, and in a wide range of driving rates for quasistatic and finite-rate driving, providing an extensive overview and comparison of the joint effects that the disorder, type of driving, and rate regime have on the system's behavior.