Ordering in magnetic multilayers by off-specular neutron scattering

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.