Two dimensional models for Barkhausen noise

Abstract

We analyze the current experimental and theoretical research about the magnetization (Barkhausen) noise in magnetic thin films. We observe that, in respect to three-dimensional systems, the situation is much more complicated, and many details still have to be analyzed and understood. In particular, the critical exponents must be correctly analyzed when compared with the theoretical predictions. We observe, for instance, that the measured magnetization steps in optical measurements do not actually correspond to the avalanche size, as claimed, but to a different quantity having a different critical exponent. We also observe as the lack of a significative demagnetizing field does not assure to have a stationary Barkhausen signal, which again implies a different set of exponents. For comparison, we report in detail all the possible theoretical values of the critical exponents calculated for a single DW model.

The role of stationarity in magnetic crackling noise

“…Nevertheless, this scientific field is still very active, also because the Barkhausen effect is generally considered as one of the cleanest examples of crackling noise [1]. A detailed analysis of the vast scientific literature on the subject can be found in our recent review [11]. Our main conclusion is that, despite the large variety of soft magnetic materials, most of the experimentally measured scaling exponents can be grouped into two different universality classes, reflecting the dominating magnetic interactions [12].…”

“…In [11], we have analysed many experimental papers in the literature to establish a set of practical rules to be able to compare experimental data with the theoretical predictions. A fundamental experimental condition is to utilize a setup which ensures the stationarity of the noise signal.…”

“…The details of the experimental setup have been described at length in other papers [11,12]. Essentially, a 30 cm solenoid provides a constant applied field all along the sample.…”

Barkhausen noise from zigzag domain walls

“…Until now, most of the models and experiments on BN have focused on three dimensional systems [5]. The difficulties for the study of two dimensional samples, in fact, concern both the theoretical and the experimental aspects of the problem.…”

“…The models currently used for three dimensional materials could be classified in two main groups, namely spin models of the Ising type [7]- [10], and single domain wall models [11]- [16]. On the experimental side, the inductive experimental set-up commonly used for bulk samples [5] is usually not suitable for thin films, due to the low intensity of the magnetic flux variation signal, which is roughly proportional to the sample thickness, and thus tends to vanish for very thin films. Conversely, the magneto-optical [17]- [19] and magneto-optical microscope magnetometry [20] experiments, though able to supply the domain structure, that is not accessible via inductive measurements, provide only partial information about the probed zone, and not about the whole sample.…”