Sm Atoms Research Articles

ＳｍｘＢａ１−ｘＣｕＯｙの微細構造と磁束線のピン止め効果

The substitution for the Ba sites in Sm1/3Ba2/3CuOy (=SmBa2Cu3Oy) by Sm induces the local oxygen disordering in the Cul-O planes since the Sm atoms located on the Ba sites are apt to have eight oxygen coordination. In order to investigate the effectiveness of the disordered oxygens as pinning centers for flux lines in SmxBa1-xCuOy, the magnetic hysteresis curves were examined by SQUID magnetometer. As a result, the critical current density Jc, which is estimated from the magnetic hysteresis curves, decreased with increase of degree of the oxygen disordering in the Cul-O planes of SmxBa1-xCuOy. Thus, the disordered oxygens do not act as effective pinning centers. This result is in contrast to the result in YBa2(Cu1-xFex)3Oy system where the Jc has the maximum value at about x=0.02, and indicates that the increase of Jc in the YBa2(Cu1-xFex)3Oy system is ascribed not to the disordering oxygens, but to the clustered Fe atoms.

Mössbauer effect study on magnetic properties of intermetallic compounds (Sm 1—xY x) 2Fe 17N y

Mössbauer spectroscopy was used to study the substitution effect of Y for Sm atoms and the occupation of N atoms in (Sm 1—xY x) 2Fe 17N y ( x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0; 2 < y <3). Our results show that the N atoms in these nitrides occupy not only 9 e sites but also 3 b sites. The experimental results have confirmed the following facts. (1) The crystal structure changes when x exceeds 0.5. (2) The average magnetic hyperfine fields at the different iron sites in (Sm 1—xY x) 2Fe 17N y vary with the yttrium concentration. (c) (Sm 1—xY x) 2Fe 17N y compounds display an easy c axis anisotropy as the yttrium content ranges from x = 0 to 0.8 according to the Mössbauer fitting results.

Valence state and electronic structure of the misfit-layer compound SmNbS3

X-ray photoemission, X-ray absorption and reflection electron-energy-loss spectra of SmNbS3 have been measured for the first time. The results give no clear evidence for valence fluctuation or the occurrence of mixed-valence states for Sm atoms. The Sm 4d and 3d X-ray photoemission spectra suggest that Sm exists mainly as a trivalent ion like the pressure-induced metallic phase of SmS, in agreement with a recent lattice parameter measurement. The author has estimated that the number of Sm2+ ions is less than a few per cent of the number of Sm3+ ions, if they exist. Charge transfer from SmS layers to the incompletely filled Nb d(z2) band of NbS2 layers has an important effect on the valence state of Sm and the disappearance of a shoulder near the Nb L2 X-ray absorption edge. The Sm N4,5 inner-shell-electron-energy-loss spectrum exhibits non-optical transitions below the threshold, as has already been observed for the elemental metal Sm. The valence and conduction bands are also discussed.

Structure of K3Na4H2[TbW10O36].20H2O

0.394 (4) 0.25 0.08 (2) 069 0.212 (2) 0.421 (3) 0.0366 (10) 0.09 (1) 070 0.152 (2) 0.576 (3) 0.0513 (10) 0.11 (2) O71 0.052 (3) 0.352 (4) 0.222 (1) 0.17 (2) Abstract Tripotassium tetrasodium dihydrogen decatungstosama- rate docosahydrate, K3NaaH2(SmWI0036 ).22H20, con- sists of a decatungstosamar ate anion, three sevenfold or eightfold coordinated potassium cations, four octahe- drally coordinated sodium cations, and water molecules. The decatungstosamar ate anion is comprised of two W50~- moieties chelating to a central Sm 3÷ cation, which lies in a tetragonal antiprismatic coordination field. The Sm atom is not at the midpoint of the two W506~ - groups. The Sm--W distances are 3.820-3.840 A for the W atoms in one group and 3.855-3.888 ~, for those in the other.

Calculated Electronic Structure and Magnetic Properties of a New Ternary Rare-Earth-Iron Nitride R2Fe17N3

Electronic structure and magnetic properties of a new permanent magnetic material R2Fe17N3 (R=Sm or Nd) have been studied with self-consistent, spin polarized local spin density functional theory calculation. Several cluster models were used to study the electronic structure of this system. The location of nitrogen atoms was determined by total energy calculation for clusters with various possible N sites in crystal. The distribution of electrons and the magnetic moments for four kinds of inequivalent Fe atoms have been obtained. The s - d (s - f) exchange interaction for different Fe sites and Sm atoms was also evaluated. The role of nitrogen atoms in R2Fe17Nδ (δ=0, 3) was discussed.

Electronic structure and magnetic properties of R 2Fe 17N 3

Self-consistent, spin-polarized local spin density functional theory calculations have been performed for Sm 2Fe 17N 3, a new permanent magnetic material. Several cluster models were used to study the electronic structure of this system. The locations of nitrogen atoms was determined by total energy calculation. The s-d (s-f) exchange interaction for different Fe sites and Sm atoms was also evaluated. The role of N atoms in R 2Fe 17N 3−δ was discussed.

Rare-earth growth structures on GaAs(110): Ce, Sm, and Yb.

Adsorption of the rare-earth metals Ce, Sm, and Yb on GaAs(110) at 300 K produces two bonding structures. Dual-bias scanning-tunneling-microscopy results for coverages below \ensuremath{\sim}0.1 monolayer indicate that one, termed an A site, is dominated by unoccupied states while the other, a B site, is rich in both occupied and unoccupied states within the tunneling bias range. Sm and Yb atoms in A sites form zigzag chains of five to ten atoms along the surface [11\ifmmode\bar\else\textasciimacron\fi{}0] direction while Ce atoms in A sites appear isolated. Ce, Sm, and Yb atoms in B sites form structures that are dominated by linear chains along [11\ifmmode\bar\else\textasciimacron\fi{}0]. Disordered structures were readily observed for all three systems because of interfacial reaction by \ensuremath{\sim}0.3-monolayer deposition.

Sm/GaAs(110) interface formation: Surface instabilities and kinetic constraints

Synchrotron radiation photoemission results for Sm/GaAs(110) interfaces formed and studied at 20 and 300 K show temperature dependencies that can be related to differences in surface growth structures and kinetic constraints. Submonolayer growth at 300 K produces two distinct ordered Sm chain configurations, as shown by scanning tunneling microscopy, and the photoemission results demonstrate that Sm atoms in these chains are divalent. These low‐surface‐density divalent configurations are precursors to surface disruption that, with additional Sm deposition, produce reacted clusters in which the Sm atoms are trivalent. Ultimately, Sm metal nucleation occurs on the reacted region and the overlayer thickens, with Ga and As atoms segregating to the surface region. For 20‐K growth, the valence‐band results show much slower conversion from divalent to trivalent Sm bonding, despite evidence that the amount of disruption is equivalent at 20 and 300 K. We attribute these differences, and those in the Ga and As core levels, to the freezing‐in of an amorphous Sm–Ga–As mixture at 20 K. Hence, kinetic factors curtail atom rearrangements that occur readily at 300 K. Annealing of thin overlayers to 300 K removes kinetic constraints and produces Ga, As, and Sm bonding that is spectroscopically equivalent to that observed for 300‐K growth. Sm/GaAs(110) interfaces formed by cluster assembly are shown to be unstable. Together, these results demonstrate that high‐atom‐density Sm contacts to GaAs are thermodynamically very unfavorable and that the instability generated by increasing the surface coverage provides the driving force for disruption.

Adsorption and interaction of Sm on GaAs(110) studied by scanning tunneling microscopy.

Scanning-tunneling-microscopy studies of the interactions of Sm with GaAs(110) at 300 K show two growth structures. Low density zigzag chains form by 0.01 monolayer (ML) with (divalent) Sm atoms bound to Ga surface atoms along the [11\ifmmode\bar\else\textasciimacron\fi{}0] direction (Sm-Sm distances 6.9 and 7.9 \AA{}). These zigzag chains are limited in length but bridge two or three substrate rows. Higher-density linear chains of (divalent) Sm atoms form at the expense of the zigzag chains with increased deposition, and the adatoms are bonded beside two Ga atoms near an As atom (Sm-Sm distance \ensuremath{\sim}4 \AA{}). Only short single chains are observed, and they convert to reacted (trivalent) clusters that bridge substrate rows at higher coverage. By \ensuremath{\sim}0.33 ML, the surface structure is composed of linear chains and reacted clusters with a small number of residual zigzag chains. Synchrotron-radiation photoemission results provide a correlation of structure with Sm valence. Comparison to Cs/GaAs(110) offers insight into low-coverage nucleation.

Enhancement of Fluorescent Intensity of a SiO2 : Sm Glass by Al Codoping and Local Structure around Sm by an EXAFS Study

Al codoped phosphors were prepared by the alkoxide method, which starts from a hydrolysis of silicon ethoxide and the metal nitrates at low temperature and minimizes the contamination of impurities. An addition of Al ions to is found to increase emission intensity from Sm ion more than an order of magnitude. EXAFS study revealed that local structures around Sm ions in the phosphors with and without dopant are significantly different; in the phosphor Sm atoms are well dispersed at low Sm concentrations and Sm atoms agglomerate at high concentrations, while in the Al codoped phosphor Sm atoms are coordinated by Al through Sm‒O‒Al bonding. This provides a direct structural evidence of the role of the codopant.

Dicyclopentadienylsamarium complexes with t-butyl substituents in the ring. Crystal and molecular structures of the solvate (η 5-C 5H 3Bu 2t) 2Sm · OC 4H 8 and homoleptic ate complex [NaSm(η 5:η 2-C 5H 4Bu t) 3 · OC 4H 8] n

Interaction of SmI 2 with C 5H 3Bu 2 tNa and C 5H 4Bu tNa yielded a monosolvate (I) with the formula (η 5-C 5H 3Bu 2 t) 2Sm · OC 4H 8 and a homoleptic ate complex (II) with the formula [NaSm(η 5:η 2-C 5H 4Bu t) 3 · OC 4H 8] n . The crystals of I are monoclinic: a 11.449(3); b 15.305(4); c 17.688(5) Å; γ 92.93(2)°; space group P2 1/ n; Z = 4; d calcd 1.24 g/cm 3. This compound is monomeric with a pseudotrigonal coordination environment around the Sm atom. The crystals of II are rhombic: a 8.969(2); b 15.964(4); c 21.701(5) Å; space group Pc2/ n; d calcd 1.30 g/cm 3. The lattice of II is built up of planar polymer grids between which crystallizational THF molecules are located.

Magnetic properties of Sm-Fe-Ti-Al sputtered films with i H c greater than 30 kOe

Recently the synthesis of a new high intrinsic coercive force, iHc=38.5 kOe at 293 K, Sm-Fe-Ti phase in film form was reported. Films with Al additions have now been made, and the preparation conditions are better defined. The addition of 2.3–4.5 at. % Al helped to sharpen the x-ray patterns of the high iHc samples. The iHc values for Al concentrations less than 4 at. % did not fall below 30 kOe for proper preparation conditions. The nominal composition for the high iHc phase samples spanned from 17 to 22 at. % Sm, and Ti/Fe ratios from 0.09 to 0.14 when related to Sm-Ti-Fe. The high iHc samples are reported to be composed of two Ti-substituted phases. The high iHc phase is found to be a SmCo5-related hexagonal structure with a nominal formula of Sm7(Fe,Ti)30. The Ti addition allows Ti to form dumbbell pairs in replacing Sm atoms. The semihard phase component is reported as a cubic Sm(Fe,Ti)2 phase. The iHc values were most sensitive to the Ti/(Ti+Fe) atomic ratio and rose at the rate of +6 kOe/%[Ti/(Ti+Fe)] as the nominal composition of 19 at. % Sm was approached and starts to decrease for higher ratios. Initial magnetization studies have been used to show the influence of the magnetic field that was applied during sputter depositions and crystallization.

High-energy product Sm-Co-based sputtered films, crystal texturing, and magnetic properties

Sm-Co-based sputtered films have been deposited that exhibit a remanence ratio for hysteresis loops measured out of the plane to in the plane of 0.04. These results have been obtained by thermalized sputtering this system in Ar, Ar+Xe mixtures, and in Xe. The use of Xe has allowed a more efficient thermalization of the massive Sm atoms so that a lower total pressure can be used than if Ar were used alone. The use of Ar-Xe mixtures as the sputtering gas has allowed high-energy product Sm2(Co, Fe, Cu, Zr)17 films with the TbCu7-type crystal structure to be obtained over a much wider range of substrate temperatures and sputtering pressures than has been possible for films sputtered only in Ar. Films sputtered in Ar will show a perpendicular to the in-plane remanence ratio of 0.36 vs 0.04 for Xe. The slope of the hysteresis loops was nearly linear from +18 to −4.5 kOe with values of −0.7%/kOe for the Xe films and a value of −1.2%/kOe for the Ar films. All of these films were directly crystallized onto heated substrates, which is necessary to control the crystal texturing.

Magnetic Susceptibility and Valence of Ce and Pr in Their Liquid Binary Alloys with Metals of the Iron Subgroup

The temperature versus concentration dependences of the magnetic susceptibility of liquid Fe, Ce; Co, Ce; Ni, Ce; Fe, Pr; Co, Pr; Ni, Pr; Fe, Sm; Fe, La; Co, La; and Ni, La alloys are given. Measurements are made by the Faraday method with the automatic pendulum scale in the temperature range from the melting point to 1650°C and REM concentrations of 0 to 100%. It is estimated that the concentration dependences of the magnetic susceptibitity have minima near equiatomic composition as a rule. The valent conditions of Ce, Pr, and Sm atoms in their alloys with Fe, Co, and Ni are estimated on the basis of the experimental data. It is found that the Ce atom valence in liquid alloys with Fe, Co, Ni, and also of Pr in melts with Co and Ni increases with increasing 3d-metal concentration. It is noted that the delocalization effects in melts are more obvious that in the similar solid systems. [Russian Text Ignored].

4d-shell photoionization of Xe, Cs, Ba, Sm, Eu and Yb atoms studied by photoion-yield spectra

A comparative study of multiple photoionization in the 4d ionization region (78-270eV) of M = Xe, Cs, Ba, Sm, Eu and Yb atoms is reported. Partial photion-yield spectra for Mn+ (n = 1-4) ions have been measured by using synchrotron radiation as a light source. Main products in Xe, Cs and Ba are Mn2+ and M3+ ions due to the creation of a 4d vacancy. In Sm and Eu, a large fraction of M+ ions are populated via the 4d-4f resonant excitation and subsequent autoionization to the 4f ionization continuum, which is squeezing the population of multiply-charged ions to about 50%. In Yb, a large amount of M+ ions are also populated, but are due largely to the direct 4f ionization. In all of the atoms studied, an appreciable or considerable amount of M4+ ions are observed, indicating the existence of photoelectron and/or Auger shake-off processes.

Redetermination of the phase equilibria in the system Sm-Co-Cu for Sm content 0–20 AT.% AT 850°C

A reinvestigation of the phase equilibria is carried out at 800°C in the system Sm-Co-Cu for Sm content up to 20 at.%. The experimentation involves the electron microanalysis and X-ray diffraction study of heat-treated specimens and some DTA. The new features exhibited are, on the binary Sm-Co limit, the existence of the compound Sm 5Co 19 with the rhomboedral structure, and on the Sm-Cu boundary, the solid state decomposition of SmCu 5 forming SmCu 6 and a phase Sm 2Cu 9 not previously identified, at about 850°C. In the Cu-rich part of the Sm-Co-Cu system, the pseudobinary phase Sm(Co 1− x Cu x ) 5 with the hexagonal CaCu 5 structure type is shown to have an existence range extended towards Sm-deficient compositions. The lattice parameters indicate that the stoichiometry departure likely results from the disordered substitution of Cu or Co atom pairs for Sm atoms in Sm(Co 1− x Cu x ) 5.

Site Occupation of Additional Elements in Sm-Co-Based Permanent Magnet by ALCHEMI

Microstructures of a commercial Sm-Co-based permanent magnet containing small amounts of Fe, Cu, and Ti were investigated by transmission and analytical electron microscopy. The magnets are composed of two compounds, Sm2(Co, Fe, Cu, Ti)17 and Sm(Co, Fe, Cu)5, including a small amount of titanium carbide. It is found that the fonner is rich in iron while the tatter is rich in copper. By atom-location channelling enhanced microanalysis (ALCHEMI), tbe Cu atoms in Sm(Co, Fe, Cu)5, are mainly located in the sites in the mixed planes composed of both Co and Sm atoms, whereas the Fe atoms in Sm2(Co, Fe, Cu, Ti)17 are located in both the dumbbell sites and the single Co atom planes of the layered stacking structure. The experimental accuracy of ALCHEMI for tbe Sm-Co multiphases containing plural additions is discussed, comparing it with rather simpler cases.

THERMOMAGNETIC EFFECT OF THE Sm-T(T = Fe, Co ) AMORPHOUS THIN FILMS IN HIGH FIELDS

The temperature dependence of magnetization at H=0.1-7T for amorphous SmxT1-x (T = Fe, Co) thin films was investigated in the range of 1.5 to 300 K. It was found that there was a maximum magnetization in the σ(T) curves, measured in the temperature rising process, for the SmxCo1-x thin films (x=0.46, 0.48, 0.54, 0.65). For the Sm-Co alloys, the temperatures, corresponding to σmax, are about 25-28 K and are independent of the composition. But the Sm-Fe amorphous alloys are different from the Sm-Co alloys, in the former the temperature corresponding to σmax depends on both the field and the composition of the alloys. In addition, it was found that there was σmin (or a repaid variation) at T≈6 K, and σ(T) decreased very slowly near room temperature. It was suggested that the thermomagnetic effect for the Sm-Co thin films at high field may be caused by the contribution of Sm moment to the magnetization, though the magnetic moment of Sm atoms is very small (≈0.1μB), and the random local anisotropy is strong at low temperatures and changes signicantly between 20-30 K. But the thermomagnetic effect of the Sm-Fe amorphous alloys may be caused by the dispersion of the Fe moments. The σmin at T≈6 K and the slow decrease of σ(T) near room temperature may be caused by fluctuation of composition in these alloys.

2-17型Sm-Co磁石の1-7相の安定化におよぼすジルコニウムの効果

The 2-17 type rare earth permanent magnets show high coercivity only when they are subjected to aging after solution treatment. It is necessary for obtaining the high coercivity that they are in a single 1-7 phase region at the solution temperature. In the present study, an isothermal phase diagram in the Sm-Zr-Co ternary system at 1473 K close to the solution temperature was constructed, in order to investigate the extent of composition ranges stable for the 1-7 phase due to Zr addition, and the behavior of the Zr atom in the 1-7 phase was investigated. It is shown that the Zr addition may fairly extend the stable 1-7 phase region to the higher Co content. Zr atom dissolved in the 1-7 phase seems to substitute either a pair of Co atoms occupying a dumbbell site or a single Sm atom involved in the 1-7 phase.

Theoretical investigation of rare-earth and barium spectra by the Hartree-Fock-Dirac method

Calculations of the electronic level structures of rare-earth and barium atoms were carried out using single- and multi-configuration approximations of the Hartree-Fock-Dirac method (HFD). Interplays between the principal atomic characteristics and the numbers of 4f electrons in Ce, Sm, Eu and Yb atoms for core and excited electrons have been considered. It was found that 4f collapse occurs at the very beginning of the lanthanum series. The importance of relativistic effects in the computation of rare-earth highly excited states was analysed.