13 In Figure 2a, we compare the rotational relaxation rate obtained by SRPAC to the sum of the rotational and translational relaxation rates obtained by NFS and Mössbauer Spectroscopy (MS) [1]. Below 190 K the data sets coincide, which means that translational dynamics is absent in the experimental time window. Above 190 K the NFS and MS data begin to deviate from the SRPAC data because translational dynamics is activated. From these results the pure translational relaxation rate can be derived.

We report the observation of nuclear resonant diffraction of synchrotron radiation by a synthetic multilayer. The nuclear period of the [Fe-57(22 angstrom)/Sc(11 angstrom)/Fe(22 angstrom)/Sc(11 angstrom)] x 25 multilayer was chosen to be twice the electronic period to obtain a pure nuclear.Bragg reflection. Strong enhancement of the radiative scattering channel provided a fast time response for the Fe-57 resonant scattering at the Bragg peak, with a decay time of 4 ns. The nuclear multilayer will be useful as a narrow bandpass monochromator for synchrotron radiation.

Epitaxial layers of 81% 57Fe-enriched Y3Fe5O12 were grown on thick, (100)-oriented substrates of Gd3Ga5O12 for experiments in resonant nuclear diffraction. Layers up to 10 μm thick were grown on each side of 32-mm-diam, 5-mm-thick wafers using techniques common for the growth of magnetic bubble materials, but with the use of a PbO-V2O5 flux in place of the usual PbO-B2O3 flux. The PbO-V2O5 flux offers a lower solubility of YIG which allows a reduction in the amount of 57Fe oxide required for layer growth. Thick substrates were used to reduce possible bowing from lattice constant mismatch. Lead incorporation onto yttrium lattice sites was controlled by adjusting the growth temperature, and this allowed a close lattice constant match between the layers and the substrate. Layer thickness was essentially uniform across the layer diameter with the edges 5% thicker than the center. Curie temperature and Faraday rotation measurements of the equivalent (111)-oriented material indicate as a formula unit (Y2.96Pb0.04)Fe3(Fe1.94Y0.06)O12. YIG/YIG double-crystal diffraction by tungsten L-γ1 irradiation of a 5×7-mm rectangular area of the first crystal gave a composite linewidth of 13 arcsec for the {400} reflection. This same linewidth was observed in synchrotron illumination of the central 80% of the area of the first layer. The possibility of linewidth reduction in this material is discussed.

The two main purposes of this work were to decide : a) are there rotational relaxation effects when diffusion becomes important above the glass transition temperature Tg ; and b) can the intensity of the MB absorption be understood in terms of glass and liquid dynamics ? We report that rotational relaxation is not seen, and that there is a rapid increase in soft modes with temperature beginning at Tg seen both by Mossbauer technique and by Raman scattering.

The two main purposes of this work were to learn (a) if rotational diffusion can be seen along with translational, and (b) is (x(T)/sup 2/) unusual as the sample is heated from a glass to a liquid. Our observations show that (a) rotational molecular diffusion is not likely ever to be observed by quadrupole relaxation and (b) that there is indeed a fast increase in (x/sup 2/) above T/sub g/. This increase is correlated with a rapid and linear increase of the number of ''soft modes'' for the liquid above the glass transition temperature.

${\mathrm{Sb}}^{121}$ isomer shifts are presented for $\ensuremath{\alpha}$-phase Pd-Sb alloys and for the compounds PdSb and Pd${\mathrm{Sb}}_{2}$. The results are compared with similar data for Pd-Sn and Pd-Au, and it is shown that they are compatible with a model in which the solute atoms are almost perfectly screened by conduction electrons.

The Mössbauer effect has been observed for Fe(57) atoms at the surface of eta Al(2)O(3). The Fe(57) is trivalent, and the quadrupole splitting found is consistent with a surface location. Anisotropy of thermal vibration relative to the surface is observed.

The solid solutions (1- x )FeTiO 3 - x Fe 2 O 3 exhibit strong ferromagnetic moments in the composition range 0.1< x <0.6. In this region cation ordering is thought to occur such that the Fe 2+ and Ti 4+ ions occupy alternate (111) layers, thus forming sublattices A[ x Fe 3+ , (1- x )Fe 2+ ] and B[ x Fe 3+ , (1- x )Ti 4+ ]. A neutron diffraction study shows that at least 95% of the Ti ions are located on the B layer but that they are not ordered within the layer. The temperature dependence of the magnetic intensities of a number of ferrimagnetic phases reveals that both sublattice moments, at zero magnetic field, fall considerably short of the theoretical values. In addition, Mössbauer patterns indicate that paramagnetic behavior persists over a rather wide temperature range below the Néel temperatures of solid solutions in which x =0.21 and x =0.33. These results are interpreted as a consequence of inhomogeneity in the magnetic structure, due to competing interactions as a result of the Ti ions being disordered within the layer. The center shift and quadrupole splitting for FeTiO 3 were measured over a wide temperature range. using these results, the Mössbauer absorption by solid solutions above their Néel points can be interpreted as a superposition of the absorption peaks of Fe 2+ and Fe 3+ .