Energetics and switching of quasi-uniform states in small ferromagnetic particles

¹ Laboratoire de Mathématique, Université d'Orsay, 91405 Orsay Cedex, France, and Centre de Mathématiques et de Leurs Applications, École Normale Supérieure de Cachan, 61 avenue du Président Wilson, 94235 Cachan Cedex, France, francois.alouges@math.u-psud.fr.
² Max Planck Institute for Mathematics in the Sciences, Inselstr. 22, 04103 Leipzig, Germany, Sergio.Conti@mis.mpg.de.
³ SISSA, International School for Advanced Studies, Via Beirut 2-4, 34014 Trieste, Italy, desimone@sissa.it.
⁴ Department of Mathematics, University of Warwick, Coventry CV4 7AL, UK.

Received: 28 October 2003

Abstract

We present a numerical algorithm to solve the micromagnetic equations based on tangential-plane minimization for the magnetization update and a homothethic-layer decomposition of outer space for the computation of the demagnetization field. As a first application, detailed results on the flower-vortex transition in the cube of Micromagnetic Standard Problem number 3 are obtained, which confirm, with a different method, those already present in the literature, and validate our method and code. We then turn to switching of small cubic or almost-cubic particles, in the single-domain limit. Our data show systematic deviations from the Stoner-Wohlfarth model due to the non-ellipsoidal shape of the particle, and in particular a non-monotone dependence on the particle size.