Samarium Atoms Research Articles

Mechanism of Sintering in Cobalt Rare-Earth Permanent-Magnet Alloys

Observations of composition, temperature, and time effects during the sintering of cobalt-samarium permanent-magnet alloys are presented. A correlation between the conditions which lead to the onset of rapid shrinkage during sintering and the conditions which lead to a high Hci is noted. A model for the mechanism of shrinkage during sintering is postulated where the slow step is the diffusion of samarium atoms in the grain-boundary regions via a samarium-atom-cobalt-vacancy cluster exchange mechanism. Furthermore, it is suggested that the ``high'' Hci structures achieved in these alloys would appear to be those with a relatively high concentration of cobalt vacancies in the grain-boundary regions.

The crystal structures of orthorhombic SmAlO 3 and of trigonal NdAlO 3

The structures of NdAlO 3 and SmAlO 3 have been refined with high precision from single crystal X-ray data. Both compounds have the perovskite-like arrangement. In the trigonal NdAlO 3 (space group R 3c ) the neodymium atoms have coordination number 12, the average NdO distance being 2.660 Å. The aluminum atoms are surrounded by a trigonally distorted octahedron, with an average AlO distance of 1.896 Å. In the orthorhombic SmAlO 3, the samarium atoms are surrounded by 12-oxygen polyhedra but the coordination is slightly less than 12. The average SmO distance is 2.658 Å. Our results indicate that with the orthorhombic → trigonal transition, the distortion of the rare earth polyhedron decreases, whereas that of the aluminum octahedron increases slightly. The overall distortion of the structure decreases. A comparison of the SmAlO 3 structure with that of its iron counterpart shows that the distortion from the ideal cubic perovskite structure is quite different. Therefore, the two compounds cannot be considered truly isostructural.

Analysis of the hyperfine structure of the ground-state multiplet of the samarium atom

Relativistic radial hyperfine structure integrals have been calculated for the ground-state configuration of the samarium atom by use of relativistic Hartree-Fock-Slater wave functions. Comparison is made with experimentally determined parameters for the dipole interaction for 147Sm and the agreement is better than 5%. The quadrupole moment for this isotope is calculated to be Q147 = -0·18(3) bn.

Light Storage in Infra-Red Sensitive Phosphors*

From experiments on samples of different thickness the amount of stored light in a particular sample of the infra-red sensitive phosphor made by activating strontium sulfide with cerium and samarium is calculated to be 2.6 × 1016 quanta per cubic cm. This corresponds, for this sample, to one quantum of light for every 8 samarium atoms or every 60 cerium atoms.