Convergent finite element methods for antiferromagnetic and ferrimagnetic materials

Normington, Hywel and Ruggeri, Michele (2023) Convergent finite element methods for antiferromagnetic and ferrimagnetic materials. Other. arXiv.org, Ithaca, NY. (https://doi.org/10.48550/arXiv.2312.04939)

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Abstract

We consider the numerical approximation of a continuum model of antiferromagnetic and ferrimagnetic materials. The state of the material is described in terms of two unit-length vector fields, which can be interpreted as the magnetizations averaging the spins of two sublattices. For the static setting, which requires the solution of a constrained energy minimization problem, we introduce a discretization based on first-order finite elements and prove its Γ-convergence. Then, we propose and analyze two iterative algorithms for the computation of low-energy stationary points. The algorithms are obtained from (semi-)implicit time discretizations of gradient flows of the energy. Finally, we extend the algorithms to the dynamic setting, which consists of a nonlinear system of two Landau-Lifshitz-Gilbert equations solved by the two fields, and we prove unconditional stability and convergence of the finite element approximations toward a weak solution of the problem. Numerical experiments assess the performance of the algorithms and demonstrate their applicability for the simulation of physical processes involving antiferromagnetic and ferrimagnetic materials.

ORCID iDs

Normington, Hywel ORCID logoORCID: https://orcid.org/0000-0001-7818-5672 and Ruggeri, Michele ORCID logoORCID: https://orcid.org/0000-0001-6213-1602;
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