The domain structure of an antiferromagnetic superlattice is studied. Synchrotron Mössbauer and polarized neutron reflectometric maps show micrometer-size primary domain formation as the external field decreases from saturation to remanence. A secondary domain state consisting mainly of at least 1 order of magnitude larger domains is created when a small field along the layer magnetizations induces a bulk-spin-flop transition. The domain-size distribution is reproducibly dependent on the magnetic prehistory. The condition for domain coarsening is shown to be the equilibrium of the external field energy with the anisotropy energy.

For the design of multicompositional materials with a spatially defined order of different components symmetric polystyrene(deuterated)-block-polybuthyl methacrylate P(Sd-b-BMA) lamellar thin films are used as a structure-directing matrix for the nanoparticle arrangement. A P(Sd-b-BMA) diblock-copolymer film spontaneously self-assembles upon annealing into a lamellar multilayer and orders the PS-coated nanoparticles, incorporated into the polymer solution prior to annealing, in a periodic lamellar structure. Specular reflection and off-specular neutron scattering were applied to determine the distribution of magnetite Fe3O4 nanoparticles in a symmetric P(Sd-b-BMA) film with a concentration of the nanoparticles of 7% of the volume fraction. From the experiments on neutron specular reflection and off-specular scattering, we obtained information about the distribution of the nanoparticles within the lamellae and about the distortion of the lamellar order of the copolymer matrix. LA026818A

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Direct evidence of the nonuniformly canted state of the spin-flop phase induced by a magnetic field applied to Fe/Cr(100) superlattices is obtained by polarized neutron reflectometry. It is unambiguously demonstrated that the magnetization of the alternating Fe layers is twisted through the multilayer stack proving a stable noncollinear configuration. The maximal tilt at the end layers progressively reduces towards the center of the multilayer. The set of tilt angles is deduced from a model-free data evaluation employing the supermatrix routine. Spin-flip off-specular scattering is determined by the in-plane magnetization fluctuations and is fitted by a theoretical model of domains.

We perform a thorough analysis of the experimental dynamic structure function measured by inelastic neutron scattering for a low-temperature (Tϭ0.65 K͒ four-layer liquid 4 He film. The results are interpreted in light of recent theoretical calculations of the ͑nonvortex͒ excitations in thin liquid Bose films. The experimental system consists of four outer liquid layers, adsorbed to two solid inner 4 He layers, which are themselves adsorbed to a graphite substrate. Relatively intense surface ͑ripplon͒ and bulklike modes are observed. The analysis of the experimental data gives strong evidence for still other modes and supports the long-standing theoretical predictions of layerlike modes ͑layer phonons͒ associated with excitations propagating primarily within the liquid layers comprising the film. The results of the analysis are consistent with the occurrence of level crossings between modes, and the existence of a layer modes for which the theory predicts will propagate in the vicinity of the solid-liquid interface. The theory and experiment agree on the detailed nature of the ripplon; its dispersion at low momenta, its fall off in intensity at intermediate momenta, and the level crossings at high momentum. Similar to experiment, the theory yields an intense mode in the maxon-roton region which is intrepreted as the formation of the bulklike excitation.

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