Low-field hysteresis in disordered ferromagnets

Abstract

We analyze low field hysteresis close to the demagnetized state in disordered ferromagnets using the zero temperature random-field Ising model. We solve the demagnetization process exactly in one dimension and derive the Rayleigh law of hysteresis. The initial susceptibility a and the hysteretic coefficient b display a peak as a function of the disorder width. This behavior is confirmed by numerical simulations d = 2, 3 showing that in limit of weak disorder demagnetization is not possible and the Rayleigh law is not defined. These results are in agreement with experimental observations on nanocrystalline magnetic materials.

Random-Field Ising Models of Hysteresis

“…Clearly in neither case is all the data collapsing onto a single curve. This would be distressing, were it not for the fact that this also occurs in 12 This section follows closely the presentation in (28). mean field theory (43) at a similar distance to the critical point.…”

“…In this section we focus on a few key ones of particular experimental significance. 12 We'll discuss the following properties obtained from the simulation • the magnetization M (H, R) as a function of the external field H.…”

Phase Transitions in a Disordered System in and out of Equilibrium

“…The key issue is the identification of a reference nonequilibrium state, instead of focusing on the jump in the saturation loop. In the low disorder phase, a discontinuous hysteresis loop corresponds to a region of the field-magnetization plane not accessible by any field history [18,19]. In this regime, it is not possible to demagnetize completely by applying a slowly varying ac field.…”

“…It being quite expensive computationally, we instead perform an approximate demagnetization using an algorithm discussed in Ref. [18] with dH 10 ÿ3 . We verified that the states have negligible differences with perfectly demagnetized ones.…”

Deaging and Asymmetric Energy Landscapes in Electrically Biased Ferroelectrics

“…Domain wall motion is known to significantly affect the dielectric, piezoelectric, and magnetic properties of ferroic materials [1][2][3][4][5]. The motion of a domain wall through the lattice can be described by a force profile which represents the distribution and strength of various pinning centers [6].…”