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Étude du couplage magnéto-électrique par des calculs ab initio

Abstract : In multiferroic magnetoelectric materials, magnetic properties can be controlled by applying an electric field and conversely. Those materials are generally divided into two classes : for the type I, ferroelectric and magnetic phase transitions are uncorrelated whereas for the type II, ferroelectricity is a consequence of a particular magnetic arrangement. In spite of numerous models, the microscopic mechanisms of the magnetoelectric coupling remain unknown. In the frame of this thesis, we have studied the mechanisms governing the magnetoelectric coupling with ab initio calculations on two multiferroic compounds : YMnO3 (type I) and MnWO4 (type II). We have developed a method to study the influence of an applied electric field on the magnetic coupling. We have also studied the influence of magnetism on phonons. For YMnO3, spin-orbit interaction is found negligible into the magnetoelectric coupling and this latter is found to be principally governed by magnetostrictives and electrostrictives effects. For MnWO4, in spite of spin-orbit interaction is found to have a small intensity into the magnetoelectric coupling, this latter remains essential for the multiferroicity of this compound. We have determined that atomic displacements induced by the electric field increase the effects on the intensity of the magnetoelectric coupling.
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https://tel.archives-ouvertes.fr/tel-00651567
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Submitted on : Tuesday, December 13, 2011 - 6:30:31 PM
Last modification on : Tuesday, February 5, 2019 - 12:12:22 PM
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  • HAL Id : tel-00651567, version 1

Citation

Julien Varignon. Étude du couplage magnéto-électrique par des calculs ab initio. Electrons fortement corrélés [cond-mat.str-el]. Université de Caen, 2011. Français. ⟨tel-00651567⟩

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