Journal of Magnetism and Magnetic Materials 258–259 (2003) 382–387 Ordering in magnetic multilayers by off-specular neutron scattering V. Lauter-Pasyuk a,b, *, H.J. Lauter c , B. Toperverg d,e , L. Romashev f , M. Milyaev f , A. Petrenko b , V. Aksenov b , V. Ustinov f a Physik Department, TU.M. unchen, D-85747 Garching, Germany b Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia c Institute Laue Langevin, B.P. 156,F-38042 Grenoble Cedex 9, France d Forschungszentrum J . ulich, IFF, D-52425 J . ulich, Germany e Petersburg Nuclear Physics Institute, Gatchina, 188350 St. Petersburg, Russia f Institute of Metal Physics, Ural Div. Russian Academy Sciences, GSP-170 18 S. Kovalevskaya Str., 62019 Ekaterinburg, Russia Abstract The combination of specular reflection and off-specular scattering with polarized neutrons gives a unique detailed information on the lateral and transverse spin-configuration of a magnetic multilayer stack. We present the first direct experimental observation of a phenomenon predicted theoretically for antiferromagnetically coupled multilayers: the twisted ground-state configuration in an external magnetic field. This twisted configuration arises due to the reduced symmetry of magnetic moments of the end layers having only one neighbor. This fact can be established directly via the qualitative analysis of the line shape of the superstructure peaks on the specular line and the related off-specular Bragg sheet. Additional quantitative evaluation of both specular reflection and off-specular scattering allows one to deduce the layer-by-layer spin configuration through the multilayer stack, as well as within the plane of the layer. The presence of spin-flip off-specular scattering means that the layer magnetization is laterally not homogeneous but is decomposed into a set of domains. The distribution of magnetic moments within each domain, the domains size and their distributions are obtained. r 2002 Elsevier Science B.V. All rights reserved. Keywords: Neutron reflection—polarized; Thin film—multilayers; Exchange coupling—non-collinear 1. Introduction The phenomenon of the giant magnetoresistance in magnetic multilayers [1,2] exists for a wide variety of magnetic films with different spacer layers. A large change in resistance is connected to the change of the alignment of the layer magnetization and depends on their relative orientation. Several reviews have been written about the physical origin of the interlayer exchange coupling [3–5], describing several different models for the coupling. These models have some common features, like, for example, the period of the coupling. Other features, like the strength of the coupling, are different from model to model. However, as it was emphasized in Ref. [6], an accurate determina- tion of the coupling requires an accurate and reliable determination of the magnetic moments orientation in each layer. The problem of the ground-state spin configuration of a finite multilayer composed of anti- ferromagnetically coupled ferromagnetic layers exposed to an in-plane external magnetic field was treated theoretically. The theory of the spin configurations as a function of the external fields, was realized for a two- fold anisotropy case [7] and the isotropic case [8]. The magnetic ordering in magnetic multilayers was experimentally studied by means of magnetometry, magneto-optics, etc. [3,9,10]. However, these methods *Corresponding author. Fax: +33-4-76-20-71-20. E-mail address: vlauter@ill.fr (V. Lauter-Pasyuk). 0304-8853/03/$-see front matter r 2002 Elsevier Science B.V. All rights reserved. PII:S0304-8853(02)01118-6