Modelling of the magnetoelastic behaviour of a polycrystalline ferrimagnetic material (original) (raw)
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Physica B: Condensed Matter, 2001
The aim of this contribution is to present and compare different techniques to model of magnetoelastic couplings. In the micromagnetic model, the elementary variable used is the magnetic moment, defined at the scale of a set of atoms. The simulation of an array of interacting atoms allows for the prediction of a realistic magnetic domain structure in a two dimensional crystal. In the multiscale approach that is presented in the second part of this article, the elementary variables are the volume fractions of domains of different orientations defined at the scale of the grain. The two approaches give descriptions of the behavior of a single crystal that can be compared. Then, by the use of homogenization techniques, the multiscale approach can be used to predict the behavior of polycrystals. r 2001 Published by Elsevier Science B.V. Keywords: Micromagnetism; Multiscale; Magnetoelastic couplings 0921-4526/01/$ -see front matter r 2001 Published by Elsevier Science B.V. PII: S 0 9 2 1 -4 5 2 6 ( 0 1 ) 0 0 9 6 0 -7
The Pursuit of Hysteresis in Polycrystalline Ferromagnetic Materials Under Stress
IEEE Transactions on Magnetics, 2009
External stresses alter the magnetic properties of ferromagnetic materials such as iron and steel, a fact that has been the basis of substantial study in nondestructive testing. Existing theories and models have so far not proven reliable or accurate enough to develop a practical means of using the developed theory relating stress and magnetization to measure biaxial strains without prior knowledge of the strain or magnetic history of the sample. A deterministic model of ferromagnetic hysteresis and the effects of external stresses in materials such as iron and steel is introduced by this study. Changes in hysteresis loops due to stress are explained via changes in the magnetocrystalline anisotropy at the crystal-unit level, and are extended to the macroscopic effects that are seen in experiments. An original equation is presented which accurately describes experimentally acquired major hysteresis loops and directly relates two parameters to the two perpendicular principal strain axes thereby providing a technique able to determine the absolute stress/strain experienced by the sample. This model will potentially enable quantitative, nondestructive stress measuring devices to be developed.
Homogenisation of magneto-elastic behaviour: from the grain to the macro scale
Computational & Applied Mathematics, 2004
The prediction of the reversible evolution of macroscopic magnetostriction strain and magnetisation in ferromagnetic materials is still an open issue. Progress has been recently made in the description of the magneto-elastic behaviour of single crystals. Herein, we propose to extend this procedure to the prediction of the behaviour of textured soft magnetic polycrystals. This extension implies a magneto-mechanical homogenisation. The model proposed is discussed and the results are compared to experimental data obtained on industrial iron-silicon alloys. Mathematical subject classification: 74F15, 74Q05, 74Q15, 74M05, 78M40.
A multiscale model of magnetostriction strain and stress effect
Journal of Magnetism and Magnetic Materials, 2001
The aim of this paper is to predict the reversible evolution of macroscopic magnetostriction strains and magnetisation in textured non-oriented soft ferromagnetic materials. The model takes account of both the domain wall displacements and the magnetisation rotations. The anisotropic macroscopic behaviour is derived from a statistical description of the magnetic domain structure by homogenisation techniques.
Phase Field Crystal Model for Magneto-Elasticity in Isotropic Ferromagnetic Solids
A new isotropic magneto-elastic phase field crystal (PFC) model to study the relation between morphological structure and magnetic properties of pure ferromagnetic solids is introduced. Analytic calculations were used to determine the phase diagram and obtain the relationship between elastic strains and magnetization. Time dependent numerical simulations were used to demonstrate the effect of grain boundaries on the formation of magnetic domains. It was shown that the grain boundaries act as nucleating sites for domains of reverse magnetization. Finally, we derive a relation for coercivity versus grain mis-orientation in the isotropic limit.
On the Magnetization Mechanisms in Polycrystalline
2018
An attempt was made to adapt the domain-wall size model to the explanation of magnetization mechanisms in real polycrystalline hard ferrites (SrFelzOle). Some new data concerning the total anisotropy specifically for polycrystals were discussed and its value deduced from natural spin resonance measurements. It was observed that samples with different Heg grain size and shape, can present different hysteresis loops. To explain these differences, we applied the theoretical expressions for the magnetization curve and the hysteresis loop developed earlier. In spite of the quickly broadening area of application of polycrystalline highly anisotropic femtes, the theory still lags behind in explaining their specific magnetization behavior [I]. A good description of the magnetization processes from the viewpoint of the grain size in isotropic ferrite structures is provided by the Globus-Guyot model 121, which considers the single crystallite as a sphere divided by a Bloch domain wall @W) mov...
Influence of the shape of the grain on the magnetization curve and the ferromagnetic hysteresis loop
Journal of Magnetism and Magnetic Materials, 1986
We have obtained theoretical expressions for the magnetization curve and hysteresis loop of polycrystalline ferrimagnets which include the effect of the shape of the grains in the sample. We obtained the expressions in terms of the ratio fl = a/c, where a and c are the semiaxes of an ellipsoid of revolution. We find a strong dependence of the area: enclosed by the hysteresis loop on the shape of the grain, i.e., on the value of ft. The slope of the initial reversible part of the magnetization curve and the magnetization curve itself also depend strongly on the value of ft.
IEEE Transactions on Magnetics, 1987
The mechanical behaviour of ferromagnetic materials must be modelled for such comulex uroblems as noises or vibrations of electric machines . The difficulties concerning that aim are defined. Then the various causes of Magnetostriction are presented. This paper focuses on magnetic forces . On this point, several theories are presented, and the most exciting are discussed, compared and developped. Indeed many doubts arise about the distribution of Magnetic force density, because diverse solutions are proposed and none appear certain. A synthesis is made between two of the most coherent approaches relying on energy methods. Then, formulations simple enough to be computed easily, are deduced. The proposed applications are detailed, providing the reader with corresponding volume force densities, associated stress tensors and surface forces densities, thus inviting practical verifications. As this paper limits itself to theory, only a few observations on this latter point will follow.