Brigitte Bidégaray-Fesquet — Micromagnetism

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Previous work

Micromagnetic objects are important issues for applications to nano-electronics, magnetic recording or characterization. Modelling the magnetization of such small objects should allow to optimize their performance in complex systems At this scale, there is a need for very precise models with established theoretical grounds and until now the transistion for these materials from the atomic to the mesoscopic scale has not been studied mathematically yet. Physicists are however highly interested in understanding the exact link between ab initio models and mesoscopic models which are the only of practical use for modellig complex systems.

The Landau–Lifschitz–Gilbert equation is a macroscopic model which describes the time evolution of the magnetization. It involves a damping term with a phenomenological coefficient α. Our goal is to construct a mesoscopic model and pass to the macroscopic scale hoping to find the origins and size of α.

This work is supported by the RTRA Nanoscience project HM-MAG (Hytérésis et Modélisation des micro-objets MAGnétiques) which also deals with hysteresis issues.

Ongoing work

We are currently working on

• the homogeneization of a lattice of dipoles in the staionary case to derive the exchange term (paper in preparation);
• the definition of a microscopic model and the mesoscopic limit.