PACS 61.05.fg -Neutron scattering including small-angle scattering PACS 75.25.+z -Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source X-ray scattering, etc.

Based on experimental magnetic-field-dependent neutron scattering data, we have calculated the autocorrelation function of the spin misalignment of nanocrystalline (160)gadolinium. The analysis suggests the existence of two characteristic length scales in the spin system: the smaller one is about 5 nm and is attributed to the defect cores of the grain boundaries, whereas the larger length scale is of the order of the average crystallite size D = 21 nm and presumably describes the response of the magnetization to the magnetic anisotropy field of the individual crystallites.

PACS 75.50.Tt -Fine-particle systems; nanocrystalline materials PACS 75.25.+z -Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source X-ray scattering, etc.) PACS 61.05.fg -Neutron scattering (including small-angle scattering)Abstract -We report magnetization and magnetic neutron scattering measurements on nanocrystalline Fe which was prepared by means of the inert-gas condensation technique. Depending on the compaction pressure applied during the synthesis procedure (0.5-1.8 GPa), the resulting Fe samples contain porosity with volume fractions between about 20-35%. We provide evidence that the spin disorder which is associated with porosity has a strong influence on magnetic properties, and it gives rise to a characteristic clover-leaf-shaped angular anisotropy in the elasticmagnetic-scattering cross-section.