Micromagnetics

 

Motivation

The sub-micron magnetic systems are very promising from applicative point of view (sensor, MRAM, recording heads). The deep understanding of the magnetic behavior of such confined system combines simultaneously experimental and numerical micromagnetism.

Solution

The micromagnetic simulation allow us to predict with high accuracy the dynamic of the magnetization at nanometric scale. Phenomena as magnetization reversal process can be described by time integration of Landau-Lifshitz-Gilbert equation.

Our numerical codes, based on finite difference approximation, are very flexibles and may deal with 2D and 3D problems periodic (Fig. 1) and non-periodic (Fig. 2). Depending on the specific properties of the magnetic systems new features may be added : for MRAM cells the the spin polarized current or for MR reading heads the perfect shields.

Aims

Several topics are preferred:
-  development of numerical tools for micromagnetic simulation based on finite difference approximation
-  improvement of existing tools (reduce the computation time, choose the stable integration schemes,..)
-  testing against benchmark problems
-  investigation of small magnetic objects direct coupled to experimental data

Team

-  Jean-Christophe Toussaint
-  Liliana Buda-Prejbeanu
-  Kyung -Jing Lee

Main publications

-  L. D. Buda, I. L. Prejbeanu, U. Ebels, K. Ounadjela Micromagnetic simulations of magnetization in circular cobalt dots Computational Material Science 24 (1-2), 181-185 (2002)

-  O. Fruchart, J.-P. Nozières, B. Kevorkian, J.-C. Toussaint, D. Givord F. Rousseaux, D. Decanini, and F. Carcenac High coercivity in ultrathin epitaxial micrometer-sized particles with in-plane magnetization: Experiment an numerical simulation Phys. Rev. B 57, 2596 (1998)

K.-J. Lee, W. Park, T. Kim Kink-free design of submicrometer MRAM cell IEEE Transaction on Magnetics 39 (5) 2842 (2003)


Fig.1
Magnetic state of a multi-track AMR head.

Fig.2
Possible stable states in circular Co dots at zero field.