Spin diffusion on a spin polarized cluster

Application to the ferromagnetic surface case

R. Lahreche1*, R.-J. Tarento2, P. Joyes2, J. Van de Walle2, D. E. Mekki1

1 Faculté des Sciences, Département de Physique, Université de Annaba BP12 Annaba, Algérie

2 Laboratoire de Physique des Solides bât 510 Université d'Orsay 91405 France

* Corresponding author. E-mail : grah_a@yahoo.fr

Received : 03 July 2002; revised version accepted : 15 September 2002

Abstract

We investigate the diffusion of a spin polarized projectile on a ferromagnetic spin polarized cluster or surface. The interaction between the projectile and the target is described with a Heisenberg Hamiltonian which excludes the charge degree of freedom during the process. To valid our formalism we discuss this assumption by making a comparison for a linear 3 atom chain between the results obtained with the Heisenberg Hamiltonian and the Hubbard Hamiltonian which adds the possibility of charge transfer. Our calculation is based on a real time description of the spins of the two interacting systems. We deduce from it the depolarized change of the projectile and the excitation in the cluster versus its size, the impact parameter and the velocity. We analyze three different behaviors of the system according to whether the intra-cluster excitations propagate slower or faster than the projectile. The depolarisation cross section has been investigate for different cluster size and projectile velocties. We apply this method to derive the depolarization in the case of spin diffusion on a ferromagnetic surface.

Keywords : Diffusion; Spin; Cluster; Ferromagnetic; Depolarization .

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