Metallic Samarium Research Articles

SmLγ1emission spectra of samarium compounds

The Sm $L{\ensuremath{\gamma}}_{1}$ emission spectra of metallic samarium, ${\mathrm{Sm}}_{2}$${\mathrm{O}}_{3}$, Sm${\mathrm{B}}_{6}$, SmS, and SmSe were measured with high precision by using a two-crystal spectrometer with the fluorescence excitation method. The $L{\ensuremath{\gamma}}_{1}$ spectrum is accompanied by the structure designated as the $L{\ensuremath{\gamma}}_{9}$ on its lower-energy side, which has been interpreted as being due to the interaction between the unpaired $4f$ electrons and the $4d$ hole produced upon the $L{\ensuremath{\gamma}}_{1}$ emission. The present results exhibit no noticeable difference in the $L{\ensuremath{\gamma}}_{1,9}$ spectrum among the substances in which the samarium ions are either trivalent or divalent. It is discussed whether this fact is inherent to the x-ray emission spectrum or the present results are indicative of a valence change due to the influence of the inner core hole.

Absence of anomalously large conduction-electron polarization in superconducting rare-earth ternary compounds

An analysis of the paramagnetic susceptibility of Sm${\mathrm{Rh}}_{4}$${\mathrm{B}}_{4}$ indicates that conduction-electron polarization effects are relatively small in the $R{\mathrm{Rh}}_{4}{\mathrm{B}}_{4}$ compounds, where $R$ is a rare earth. The coexistence of superconductivity and magnetism is therefore allowed by the smallness of the exchange interaction between the rare earth and the conduction electrons. An expression for the paramagnetic susceptibility of metallic samarium compounds is successful in explaining recent measurements on polycrystalline rhombohedral samarium metal.

Synthesis of new luminescent materials activated with divalent samarium

A simple technique for the preparation of powder compounds doped with divalent samarium is described. The reaction is carried out in nickel containers sealed in an inert atmosphere. The samarium impurity is introduced as samarium trifluoride SmF 3, and metallic samarium powder acts as the reducing agent to change Sm 3+ into Sm 2+. Using this method, samarium has been stabilized in the divalent state in various fluorides: KMgF 3, BaLiF 3, BaY 2F 8, and KY 3F 10. The resulting compounds show under ultraviolet or visible excitation an intense luminescence in the red region characteristic of Sm 2+-doped materials. The emission and excitation spectra of these phosphors are presented and briefly discussed.

Divalent Surface State on Metallic Samarium

It is shown that the first atomic layer of trivalent metallic samarium has a large divalent component. The valence transition is attributed to a narrowing of the 5d band which populates the low-lying 4f/sup 6/ state.

Gyromagnetic Ratios of Metallic Samarium Compounds

In metallic rare-earth compounds the exchange interaction between the $4f$ shell and the conduction electrons causes a portion of the conduction-electron magnetization to be added to the magnetization of each rare-earth atom. Because these two magnetization components will, in general, have different gyromagnetic ratios, it follows that the gyromagnetic ratio of the whole material will differ from that of the rare-earth ions alone, which is given by the Land\'e factor. For the rare-earth metals apart from samarium, the resulting gyromagnetic ratio shifts are estimated to be of the order of 1%, too small to be detected by present experimental methods. However, an exploratory calculation suggests that the shift might be very large, perhaps of the order of 100%, in a samarium compound in which the interactions were of a strength comparable to those which are found in elemental samarium metal.

Magnetic Structures of Samarium

The magnetic structures of metallic samarium have been determined from neutron-diffraction data on a single crystal of $^{154}\mathrm{Sm}$. Anomalies in a number of physical properties of this metal at 106 and 13.8\ifmmode^\circ\else\textdegree\fi{}K are associated with ordering of the moments on the hexagonal and cubic sites, respectively. The unusual form factor expected for a $4{f}^{5}$ configuration has been observed. Striking evidence for important conduction-electron polarization effects has been found.

Paramagnetic Susceptibilities of Metallic Samarium Compounds

It is shown that the influence of conduction-electron polarization effects upon the susceptibilities of metals containing the tripositive samarium ion is very much greater than upon metals containing normal rare earths. A theory of the susceptibility of metallic samarium materials is developed which takes account of these polarization effects and of interionic Heisenberg exchange couplings, the admixture of the $J=\frac{7}{2}$ state into the $J=\frac{5}{2}$ ground state, which is assumed to be the only one to be thermally populated, but which, however, does not take account of crystal-field splittings. The susceptibility is found to be of the unexpectedly simple form $\ensuremath{\chi}(T)={\ensuremath{\chi}}_{0}+\frac{D}{(T\ensuremath{-}\ensuremath{\theta})}$, in which the only dependence on temperature $T$ is that explicitly shown. This expression is found to fit the published data for the susceptibility of dhcp samarium to an accuracy of 1% in the temperature region 110-230 \ifmmode^\circ\else\textdegree\fi{}K, and the parameters extracted from the fit are found to be in excellent agreement with those obtained for the other light rare-earth metals. An expression is also derived for the susceptibilities of metals containing normal rare earths, which takes account of both conduction-electron polarization and crystal field effects.

High temperature phase equilibria in the systems Sm 2O 3WO 3 and Sm 2O 3WWO 3

Using the sealed capsule technique, the system SmWO has been studied at high temperatures with emphasis on the formation and stability of ternary phases. The equilibrium relations in the region Sm 2O 3WWO 3 at 1700°C and along the join Sm 2O 3WO 3 were determined in detail. Three ternary phases were found to be stable at high temperatures. They are 3Sm 2O 3·WO 3, and 7Sm 2O 4·4WO 3 with melting points of 2240 and 2190°C, respectively, and Sm 2O 3·WO 3, which melts incongruently at 1690°C. Two low temperature phases, Sm 2O 3·2WO 3 and Sm 2O 3·3WO 3, were also formed in the system, and melt at 1245 and 1155°C, respectively. The reaction between the platinum capsule and metallic samarium, which destroys the sealed system, prevented the collection of reliable phase data for the SmSm 2O 3W compositional range of the system. Experiments on alloying tungsten and samarium in hydrogen also failed to produce significant data for the WSm join due to the loss of samarium at high temperatures. No attempt has been made to determine the actual pressure and the partial pressure of oxygen necessary to maintain the condensed phase equilibrium relations shown. Generalities governed by thermodynamics and the phase rule are stated.

Paramagnetic Behavior of Polycrystalline Samarium from 300°K to 1400°K

The paramagnetic susceptibility of polycrystalline samarium metal has been measured as a function of temperature between 300 and 1400\ifmmode^\circ\else\textdegree\fi{}K. The high-temperature phase transformations do not produce noticeable discontinuities in the magnetic susceptibility, indicating that the interactions between the samarium ions are small at these temperatures. The experimental results are compared with the Van Vleck theory of paramagnetism. It appears that the energy levels of ${\mathrm{Sm}}^{+++}$ in metallic samarium differ more from those predicted by the Russell-Saunders coupling than has been realized before. Collective magnetic behaviors resulting from the interactions between the samarium ions are briefly discussed in the light of some recent low-temperature investigations.