Spin dynamics across an inhomogeneous atomic boundary separating ultrathin Heisenberg ferromagnetic films

¹ Département de Physique, Faculté des Sciences, Université Mouloud Mammeri de Tizi-Ouzou, BP 17 RP, 15000 Tizi-Ouzou, Algeria
² Department of Physics, McGill University, 3600 rue University, Montreal, QC Canada H3A 2T8
³ Laboratoire de Physique de l'État Condensé, UMR 6087, Université du Maine, 72085 Le Mans, France
⁴ School of Sciences, Lebanese American University, PO Box 36, Byblos, Lebanon

Corresponding authors: mbelhadi@yahoo.com antoine.khater@univ-lemans.fr

Received: 18 November 2005
Revised: 25 May 2006
Accepted: 28 August 2006
Published online: 8 November 2006

Abstract

A theoretical model is presented for the study of the scattering and the localisation of spin-waves at an extended inhomogeneous structural and magnetic boundary separating ultrathin Heisenberg ferromagnetic films. The model system consists of two different magnetic materials A and B with different thickness of two and three atomic layers, on either side of a defect atomic step. The matching technique is used with nearest neighbour magnetic exchange to analyse both the localisation and the scattering spin dynamics. The localised spin states that manifest themselves as Rayleigh branches, and the local densities of spin states are calculated on this boundary. The coherent reflection and transmission scattering properties of spin-waves incident from the interior of the ultrathin films on the inhomogeneous boundary are also calculated. The numerical calculations are applied in particular to a system of three Fe ferromagnetic atomic layers and two Gd ferromagnetic atomic layers, across a defect atomic step. The results illustrate the occurrence of Fano resonances in the transmitted spectra due to the localised spin states on the inhomogeneous boundary. An interesting physical effect is observed for this magnetic and atomic step boundary, namely the frequency selective conductance of the spin-waves via Fano resonances, by an appropriate choice of the angle of spin-wave incidence on the boundary.