In electromagnetism and materials science, the JilesâÂÂAtherton model of magnetic hysteresis was introduced in 1984 by David Jiles and D. L. Atherton. This is one of the most popular models of magnetic hysteresis. Its main advantage is the fact that this model enables connection with physical parameters of the magnetic material. JilesâÂÂAtherton model enables calculation of minor and major hysteresis loops. The original JilesâÂÂAtherton model is suitable only for isotropic materials. However, an extension of this model presented by Ramesh et al. and corrected by Szewczyk enables the modeling of anisotropic magnetic materials.
Magnetization of the magnetic material sample in JilesâÂÂAtherton model is calculated in the following steps for each value of the magnetizing field :
Original JilesâÂÂAtherton model considers following parameters:
Extension considering uniaxial anisotropy introduced by Ramesh et al. and corrected by Szewczyk requires additional parameters:
Effective magnetic field influencing on magnetic moments within the material may be calculated from the following equation:
This effective magnetic field is analogous to the Weiss mean field acting on magnetic moments within a magnetic domain.
Anhysteretic magnetization can be observed experimentally, when magnetic material is demagnetized under the influence of constant magnetic field. However, measurements of anhysteretic magnetization are very sophisticated due to the fact, that the fluxmeter has to keep accuracy of integration during the demagnetization process. As a result, experimental verification of the model of anhysteretic magnetization is possible only for materials with negligible hysteresis loop.<br /> Anhysteretic magnetization of typical magnetic material can be calculated as a weighted sum of isotropic and anisotropic anhysteretic magnetization:
Isotropic anhysteretic magnetization is determined on the base of Boltzmann distribution. In the case of isotropic magnetic materials, Boltzmann distribution can be reduced to Langevin function connecting isotropic anhysteretic magnetization with effective magnetic field :
Anisotropic anhysteretic magnetization is also determined on the base of Boltzmann distribution. However, in such a case, there is no antiderivative for the Boltzmann distribution function. For this reason, integration has to be made numerically. In the original publication, anisotropic anhysteretic magnetization is given as:
where
It should be highlighted, that a typing mistake occurred in the original Ramesh et al. publication. As a result, for an isotropic material (where ), the presented form of anisotropic anhysteretic magnetization is not consistent with the isotropic anhysteretic magnetization given by the Langevin equation. Physical analysis leads to the conclusion that the equation for anisotropic anhysteretic magnetization has to be corrected to the following form:
In the corrected form, the model for anisotropic anhysteretic magnetization was confirmed experimentally for anisotropic amorphous alloys.
In JilesâÂÂAtherton model, M(H) dependence is given in form of following ordinary differential equation:
where depends on direction of changes of magnetizing field ( for increasing field, for decreasing field)
Flux density in the material is given as:
where is magnetic constant.
Vectorized JilesâÂÂAtherton model is constructed as the superposition of three scalar models one for each principal axis. This model is especially suitable for finite element method computations.
The JilesâÂÂAtherton model is implemented in JAmodel, a MATLAB/OCTAVE toolbox. It uses the Runge-Kutta algorithm for solving ordinary differential equations. JAmodel is open-source is under MIT license.
The two most important computational problems connected with the JilesâÂÂAtherton model were identified:
For numerical integration of the anisotropic anhysteretic magnetization the GaussâÂÂKronrod quadrature formula has to be used. In GNU Octave this quadrature is implemented as quadgk() function.
For solving ordinary differential equation for dependence, the RungeâÂÂKutta methods are recommended. It was observed, that the best performing was 4-th order fixed step method.
Since its introduction in 1984, JilesâÂÂAtherton model was intensively developed. As a result, this model may be applied for the modeling of:
Moreover, different corrections were implemented, especially:
JilesâÂÂAtherton model may be applied for modeling:
It is also widely used for electronic circuit simulation, especially for models of inductive components, such as transformers or chokes.