3D-2D asymptotic analysis for micromagnetic thin films

Alicandro, Roberto; Leone, Chiara

ESAIM: Control, Optimisation and Calculus of Variations, Tome 6 (2001), pp. 489-498.

$\Gamma$-convergence techniques and relaxation results of constrained energy functionals are used to identify the limiting energy as the thickness $\epsilon$ approaches zero of a ferromagnetic thin structure ${\Omega }_{\epsilon }=\omega \times (-\epsilon ,\epsilon )$, $\omega \subset {ℝ}^2$, whose energy is given by

$${ℰ}_{\epsilon }\left(\overline{m}\right)=\frac{1}{\epsilon }{\int }_{{\Omega }_{\epsilon }}\left(W(\overline{m},\nabla \overline{m})+\frac{1}{2}\nabla \overline{u}·\overline{m}\right)\mathrm{d}x$$

subject to

$$\text{div}(-\nabla \overline{u}+\overline{m}{\chi }_{{\Omega }_{\epsilon }})=0\text{on}{ℝ}^3,$$

and to the constraint

$$|\overline{m}|=1\text{on}{\Omega }_{\epsilon },$$

where $W$ is any continuous function satisfying $p$-growth assumptions with $p>1$. Partial results are also obtained in the case $p=1$, under an additional assumption on $W$.

Classification : 35E99, 35M10, 49J45, 74K35
Mots clés : $\Gamma $-limit, thin films, micromagnetics, relaxation of constrained functionals

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