Model Of Ferromagnetic Hysteresis Research Articles

A two-dimensional vector model of ferromagnetic hysteresis

A new two-dimensional vector model of ferromagnetic hysteresis, which we have designated the UB model, is presented in this paper. Two types of entities constitute the model: uniaxial particles, having an energy per unit volume according to the Stoner-Wohlfarth (SW) theory, and biaxial particles that differ from the former in the magnetocrystalline energy term. The equilibrium distribution of magnetisation corresponds to an energy minimum for all particles that constitute the model. A description of the model identification is also reported. The process, although essentially different, bears some resemblance to the one used to identify the simplified Preisach model [1] (all the Preisach surface contents concentrated along the two axes of the plane) and requires knowledge of the major hysteresis loops of the specimen under study along the x and y directions. The relationship between experimental values and model parameters is obtained taking into consideration the link that is established between an SW-type particle and Preisach entities. The paper ends with examples where UB model performances are displayed.

Energetic model of ferromagnetic hysteresis

Calculations of a total energy function are used to describe a theory of hysteresis effects in crystalline, ferromagnetic materials. This model is applied on the cubic structure of FeSi crystals, which are oriented in a (110)[001] texture. The magnetic energy of the crystal is separated in reversible and irreversible parts: The reversible energy is expressed by magnetocrystalline anisotropy and shape anisotropy. They are responsible for the rotation of the domain magnetization at strong fields. At weak fields the reversible interaction of the domain wall motion with the stray fields of pinning centers (nonmagnetic inclusions, grain boundaries or inner strains) is described by a probability function of statistic domain behavior. The irreversible energy is caused by these pinning centers, too, and can be explained by the interaction losses of the magnetic moments in the Bloch wall with the crystal lattice during an irreversible Barkhausen jump. The energy of the applied field is added to these two parts and the magnetic state of the material is represented by the minima of the total energy function. The results show all features of hysteresis such as initial magnetization curve and major and minor hysteresis loops in good agreement with measurements on grain oriented 3,5% silicon-steel with Goss texture.

Considerations on the physical interpretation of the Preisach model of ferromagnetic hysteresis

The physical meaning of the standard Preisach model (PM) and of the Preisach distribution p(α,β), particularly for what concerns the problem of the characterization of magnetic interactions, is discussed. It is shown that the standard PM can only describe interactions having a net demagnetizing effect, and that, when the factorization p(α,β)=f(α)f(−β) holds, the simple relation Id/I∞ = 1 − 2√Ir/I∞, independent of f(x), exists between the Henkel plot remanences Ir and Id. These predictions are compared with recent experimental results. Finally, the relation between magnetic interactions and hysteresis loop shapes is discussed in the frame of a generalized moving PM, where the relation between the applied field Ha and the internal PM field H is of the form H=Ha+Hi(I), where Hi(I) is an odd function of the magnetization I. The shape of p(α,β) and of Hi(I) for nonoriented SiFe alloys is determined and analyzed.

Direction of change of magnetization of a ferromagnet subjected to stress

The magnetomechanical effect for a quenched and tempered alloy steel has been studied. In most published work it has been found that stress causes the magnetization to move toward the anhysteretic magnetization. However, in the present work it was found that under special conditions the magnetization moves away from the anhysteretic when a cyclic stress is applied. This behavior is tentatively explained by applying the Preisach model of ferromagnetic hysteresis.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The influence of stress on ferromagnetic hysteresis

It is argued that attempts to describe the stress magnetization behavior of ferromagnetic materials have, in general, relied upon unsubstantiated assumptions regarding the distribution of domains and the relative motion of domain walls under the combined influences of applied field and mechanical stress. An empirical description of stress-induced magnetization is presented as a practical extension of the Jiles-Atherton model of ferromagnetic hysteresis. It permits a semiquantitative description of the stress magnetization characteristics of ferromagnetic materials and highlights the profound influence of previous magnetic history. It is concluded that measuring the B/H characteristics of a material as a function of stress and invoking the Jiles-Atherton theory of ferromagnetism could provide a computational basis for predicting the magnetic behavior of complex structures under mechanical stress.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Automated measurement system to generate a Preisach-type model of ferromagnetic hysteresis

An automated measurement system for identification of ferromagnetic hysteresis based on Preisach's model is described. The data required consist of incremental permeabilities taken along symmetric hysteresis loops. Magnetic field values are determined by preset values of current in an excitation coil. Magnetic induction values are obtained using an analog integrator for the electromotive force (EMF) induced in a test coil. The integrator output is digitized. The acquisition of successive incremental permeability values as well as the data reduction and display of results are fully automatic. Details of hardware and software implementation as well as the calibration procedure and results obtained for soft iron samples of different composition are presented. The system is particularly suited to investigate the so-called statistical stability of Preisach's model by allowing use of different B-H plane scanning modes.