Temperature-dependent criticality in random 2D Ising models

Abstract

We consider 2D random Ising ferromagnetic models, where quenched disorder is represented either by random local magnetic fields (random-field Ising model) or by a random distribution of interaction couplings (random-bond Ising model). In both cases, we first perform zero- and finite-temperature Monte Carlo simulations to determine how the critical temperature depends on the disorder parameter. We then focus on the reversal transition triggered by an external field and study the associated Barkhausen noise. Our main result is that the critical exponents characterizing the power law associated with the Barkhausen noise exhibit a temperature dependence in line with existing experimental observations.

Dynamic Phase Transition in 2D Ising Systems: Effect of Anisotropy and Defects

“…To quantitatively assess the extent to which the potential defined in Equation ( 5) correlates with a site's ability to respond to the external field, we examine the local average magnetization per cycle Q i , defined in (11), for systems precisely set at the dynamic critical temperature Θ c . This serves as a means to identify a situation in which the transition between quenched and oscillating spins is in progress.…”

“…Magnetic systems, particularly the Ising spin model, provide a simple yet highly fruitful terrain for studying and understanding different dynamic phenomena [6,7]. The Barkhausen noise [8][9][10][11][12] is a paradigmatic example of bursty behavior emerging from a slow driving, and nucleation phenomena can be explored to understand how first-order transitions can be induced and driven in bistable systems [13][14][15][16].…”

Finite-Temperature Avalanches in 2D Disordered Ising Models

“…The Barkhausen noise (BN) is a classical physical phenomenon that manifests itself as a series of magnetization jumps in ferromagnetic samples as they reverse their spins under the action of a varying external magnetic field [1][2][3][4]. It bears both practical and theoretical significance, as it emerges as a macroscopic manifestation of the bursty evolution at the microscopic domain scale.…”

“…Most of the models for BN presented until now refer to zero or very low [4] temperature, whereas BN can be observed at room temperature also. The role of temperature is discussed only in few experimental or theoretical works, also within the framework of other physical phenomena exhibiting self-organised criticality [7,10,14,15].…”