[en] We show a measurement of off-specular polarized neutron scattering from an Fe/Cr/Fe trilayer inside which a second-order neutron resonance has been excited, i.e. where the probability to find a neutron was maximum at both Fe/Cr interfaces. Simulating the data in the framework of the Distorted Wave Born Approximation showed the presence of structural and magnetic fluctuations. Magnetic fluctuations in the vicinity of the Fe/Cr interfaces can be explained if one considers the anti-ferromagnetic structure of Cr and structural roughness

[en] Antisymmetric imaginary spin dependent scattering amplitudes related to atomic effects such as spin-orbit coupling, or nuclear effects such as parity violating weak forces or neutron EDM, generate particular spin rotations in perfect crystals. These effects are usually too small to be detected by normal neutron polarimetry. A new perfect crystal technique using Zeeman splitting as a polariser and termed Dual-Polarised-Beam polarimeter (DPB) with enhanced sensitivity, has been built and tested. The sensitivity of DPB to detect small spin rotations is about two orders of magnitudes better than classical polarisation techniques and it is only sensitive to antisymmetric effects. An extra gain arises from a specific enhancement effect close to the Bragg-edge directions. We have used this DPB technique in connection with a double crystal set-up to show that indeed effective electric fields up to 10⁹ V/cm are accessible in suitable crystals by measuring the spin-orbit effect arising from this field. The conditions for EDM search are discussed. (author)

[en] The distorted wave Born approximation (DWBA) is applied to evaluate the diffraction pattern of neutrons (or X-rays) from a 2D array of dots deposited onto a dissimilar substrate. With the radiation impinging on the surface at a grazing incidence angle α, the intensities diffracted both in and out the plane of specular reflection are calculated as a function of the periodicity of the array, height and diameter of the dots. The results are presented in the form of diffracted intensity contours in a plane with coordinates α and α prime, the latter being the glancing angle of scattering. The optimization of the experimental conditions for polarized neutron experiments on submicron dots is discussed. The feasibility of such measurements is confirmed by a test experiment

[en] We report on a new zero-field spin-echo spectrometer (ZETA), installed at the thermal three-axis spectrometer IN3 at ILL, Grenoble. In this technique the two long precession solenoids from neutron spin echo are replaced by two pairs of magnetic resonance coils in a zero-field region. This allows easy adaptation of tilted field geometries, necessary for measurements of phonon line widths with μeV energy resolution. First test measurements of the roton line width and energy shift as well as line width of the low-Q phonon and in the 'region beyond the roton' in superfluid ⁴He are described. The results are in agreement with the literature and show the good operation of ZETA. The implementation of ZETA at the high-flux three-axis spectrometer IN20, foreseen in the near future, will increase the count rate by typically one order of magnitude

[en] The surface layer of an epitaxial Fe/Cr multilayer system has been structured lithographically into stripes with 1 μm period. Polarized neutron reflectometry and diffuse scattering under grazing incidence measurements show strongly enhanced domain formation compared to the unstructured sample. The domains are correlated throughout the layers. The lateral domain size is partly the period of the stripe pattern of the surface layer, and partly the double

[en] A special Microsymposium on polarized neutron methods and technologies on existing and future pulsed neutron sources was held at PNCMI-2002. We present the recommendations formulated by three working groups on 'Diffraction', 'Inelastic Scattering' and 'Reflectometry'. Needs for method development as well as opportunities for novel polarized neutron instrumentation are identified

[en] A new method is presented for the direct determination of the coupling angle in magnetic exchange multilayers. Strong anomalies in the off-specular neutron spin-flip scattering intensity at critical angles give a new tool, which is tested with Fe/Cr multilayers. In addition, a complete two-dimensional data analysis of specular reflection and off-specular scattering has been employed to verify atomic spin correlation in Fe/Cr multilayers, a typical system showing the GMR effect

[en] The reflectometer REFSANS being built at the high flux reactor FRM-II in Munich is dedicated to the analysis of surfaces, interfaces and phase boundaries at the air-water interface of liquid/soft matter. Novel time-of-flight design and neutron optics have been developed to make it a most flexible device for the comprehensive analysis of samples with horizontally aligned surfaces. The potential of REFSANS for measuring low reflectivity and off-specular scattering is outlined

[en] The reflectometer REFSANS being built at the high flux reactor FRM-II in Munich is dedicated to the analysis of interfaces, phase boundaries and surfaces at the air-water interface of liquid/soft samples. Novel neutron optics have been developed for REFSANS to measure weak diffuse surface scattering most efficiently for comprehensive analyses of lateral surface structures. The machine may further be used for high-resolution SANS of bulk materials with the option of multi-beam focussing in the detector plane. Furthermore, REFSANS will allow of polarised investigations including polarisation analysis. This makes REFSANS a novel and unique tool for investigations on large-scale structures, especially for biological research projects: weak coherent scattering contributions may reliably be separated from incoherent scattering of hydrogen and comprehensive analyses of magnetic materials may be performed

[en] 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