Investigation of the magnetic structure of the diluted (Pd 0.984 Fe 0.016 ) 0.95 Mn 0.05 alloy at meso-and nanoscale levels by means of two techniques of small-angle polarized-neutron scattering (within a direct beam and beyond it) has been performed in the temperature range 10< T <60 K. The dependences of the neutron beam depolarization, the polarization rotation angle, and the polarization-dependent magnetic scattering cross section on a weak (0< H <40 A/cm) external magnetic field have been studied. A simple model of neutron beam depolarization by a sample with uniaxial magnetic anisotropy was used to analyze the results obtained. The experiment on polarized-neutron scattering in the so-called direct geometry showed the existence of a polarization-dependent scattering cross section. This scattering has left-right asymmetry and depends on temperature. Comparison of these results with the depolarization data leads to a conclusion about the existence of static chiral fluctuations in large-scale inhomogeneities.

Neutron depolarization measurements and a simple model for depolarization were used to determine the geometrical sizes of magnetic inhomogeneities in the (Pd0.984Fe0.016)0.95Mn0.05 alloy. Polarized small angle scattering shows an asymmetric part, which should be attributed to a chiral ordering of the spins.

By means of small angle neutron scattering (SANS) two different kinds of nanocrystalline materials have been investigated. From the experiment one obtains information on particle size, size distributions, shape, porosity, and interparticle arrangement. By the additional use of contrast variation techniques it is possible to suppress parasitic scattering, e.g. scattering from pores that affects the results in a conventional SANS experiment. Furthermore, contrast variation allows for the specific labelling of a certain part of sample that is of special interest. In our study SANS experiments are presented on nanocrystalline Palladium (n-Pd) and inorganic colloidal dispersions (n-TiN), where the contrast variation serves as a tool to examine the interparticle arrangement and the shape of the sorrounding stabilising organic shell.

The alloy (Fe0.65Ni0.35)1−xMnx with x = 0.11 is a re-entrant spin glass (RSG) with a strong irreversible mixed phase inside the RSG phase. In this phase the strong history dependence is shown by the size of ferromagnetic cluster on a mesoscopic length scale. To observe these mesoscopic clusters small angle neutron scattering (SANS) measurements were made. The results were fitted to squared Lorentzian and a Lorentzian with general exponent. Two different correlation lengths were found.

The early state of spinodal decomposition was studied by small angle neutron scattering in the critical mixture of the isotopic blend deutero-polystyrene/polystyrene (d-PS/PS) of equal molecular volume of 1.42×106 cm3/mol in a temperature range 12 K≤‖Tc−T‖≤82 K. This process can be described by the relaxation between two static structure factors, S(Q) representing the equilibrium values of the system in the mixed state and at the temperature where phase separation occurs. The time evolution of the relaxation process is described by the dynamical structure factor, L(Q,t) which depends on the dynamic properties of the mixture. It will be shown that the static structure factor of a mixed system can also be determined in the unstable two-phase region during the early state of spinodal decomposition. Consistent values for the Flory–Huggins parameter were found in comparison with a lower molecular d-PS/PS sample and, therefore, a lower critical temperature which was even smaller than the phase separation temperatures of the present system. The observed time evolution of the fluctuation modes is nonexponential. Therefore, it was originally supposed that internal modes of the coil come into play. The analysis of the data with an ansatz by Akcasu, which takes internal modes into account showed, however, that the phase separation in the experimental range of wave number and time is dominated by the centre of mass diffusion as in the C–H–C case and the nonexponential behavior was attributed to a time dependent increase of the ‘‘range’’ of the Onsager coefficient. A range of the Onsager coefficient larger than the radius of gyration of a single coil is predicted in case of entangled polymers. However, no time dependence was predicted so far. The evaluated diffusion constants follow an Arrhenius behavior and are consistent with earlier studies. They show a D0∝N−2 scaling consistent with reptation. A further result is the observation of a second order peak in the structure factor already in the early times of spinodal decomposition. So far, this was only attributed to the late state of spinodal decomposition.

Early state of spinodal decomposition in a symmetric isotrope mixture d-PS/PS has been studied with SANS at two temperatures well below T(c). Nonexponential time behaviour was found according to internal relaxation modes of the polymer. The data could satisfactorily be described by an ansatz from Akcasu which includes internal relaxation modes approximately and is an extension of the Cahn-Hilliard-Cook theory for polymer blends. The interaction range for the Onsager coefficient was found increasing with time and larger than the radius of gyration.