Static and dynamic susceptibilities in a disordered magnetic system

GÜLPINAR G., Özüm S., Yilmaz D.

European Physical Journal Plus, vol.141, no.7, 2026 (SCI-Expanded, Scopus)

Abstract

This study examines the steady-state kinetics of the random-field Ising model, characterized by a symmetrical bimodal discrete distribution of quenched random fields. Using a phenomenological approach based on irreversible thermodynamics, we have investigated the evolution of the order parameter in response to a sinusoidal, uniform external field perturbation. The thermal dependence of the static susceptibility is studied in detail. In addition, a rate equation governs the system’s dynamics, and the dynamic susceptibility is determined using the mean-field approximation. A detailed investigation of the dynamic susceptibility is presented across various phase transition regimes, including second-order, first-order, and tricritical point. The results show that the magnetic dispersion and absorption factors display distinct frequency-dependent patterns, characterized by symmetric divergences at low frequencies and notable dips or peaks at high frequencies. Finally, a comparison of the findings from static susceptibility with those from dynamic susceptibility shows good agreement. The results here offer insight into steady-state response mechanisms in disordered magnetic systems and improve the broader understanding of driven systems within the framework of stationary-state statistical physics.