[en] Proposed is a spectrographic method for determination of individual rare earths (Ce, Nd, Pr, La, Eu, Gd, Tb, Dy, Ho, Y) in samarium concentrates, comprizing 95-99.0% of the basic material. The method is based on the spark excitation and on the introduction of analysing substance into the excitation source in the form of the solution with the help of porous electrode. The effect of sample composition on the conditions of spectra excitation of the determining rare earths and scandium is studied. It is shown that the basic component (samarium) effects equally on the processes of rare earths and scandium excitation which permits to make a general calibrational diagram for each of analytical pairs of lines at different content of samarium (up to 5 mg/ml of Sm₂O₃) in etalons

[en] The methods of chemical X-ray phase and metallographic analyses have been used to study the homogeneity regions of samarium- and terbium selenides with the Th₃P₄ structure at 1300 and 1500 deg C. The Th₃P₄ structUre in stable in the Sm-Se system in the Sm₂Se₃-Sm₃Se₄ composition range but in the Tb-Se system it is stable in the TbSesub(1.50)-TbSesub(1.4O-1.42) composition range. Regularities in change of homogeneity regions of REE selenides are proved by calculation using the Kygimiya-Steinfink model

[en] Dependence of the electronic structure of Bsub(n9) clusters on the boron coordination number (c. n.) was investigated in the framework of the SCF-Xα-SW method. Clusters were chosen so as to contain the minimum number of atoms with all boron atoms in a cluster being equivalent. These conditions are fulfilled for the B(O), Bsub(2)(Dsub(infinityh)), Bsub(3)(Dsub(3h)), Bsub(4)(Tsub(d), Bsub(6)(Osub(h)) clusters. Peculiarity of changes of the Bsub(n) cluster structure with growth of the boron c. n. is an increase in the width of energy region of the occupied states. It is shown that the higher is the B atom c. n. the more stable is the Bsub(n) structure, which explains a high boron coordination in the crystal state. An increase in the cumulative charge and redistribution of partial charges in the atomic boron spheres with boron c. n. take place along with broadening of the energy region of occupied electron states. Calculations of the electronic structure of the SmB₂₄ cluster representing a fragment of the SmB₆ crystal has shown that single-electron energies of the interaction of bsub(2u), tsub(1u), tsub(2u) orbitals of the B₂₄ cluster with 4f-orbitals of samarium equal 0.45; 0.08; 0.06 eV, respectively. The Root-mean-square energy of these interactions is about 2.8 times as high as the energy usually accounted for in the interaction of the 4f- and 5d-orbitals of the neighbouring samarium ions

[en] Samarium-ion implantation was carried out to synthesize Sm disilicide films on silicon wafers, using a metal vapour vacuum arc ion source, and the continuous SmSi₂ films were directly obtained with neither external heating nor post-annealing. Diffraction and surface morphology analysis confirmed that the Sm disilicide films formed had good crystalline structure under appropriate experimental conditions. Also, the mechanism of formation of the SmSi₂ phase is discussed, in terms of the temperature rise caused by ion beam heating and the ion dose imparted in the process of implantation. (author)

[en] We extend a local density (LDA) calculation with self-interaction corrections (SIC) applied to black-phase SmS with six 4f-states assumed localized to the case where the valency of the Sm ion becomes a non-integer. We propose the construction of localized molecular orbital (MO) states of correct symmetry by superposition of 4f_5/2 states with a linear combination of 5d_3/2 states at the adjacent atoms. These orbitals are more extended than pure 4f-states and, therefore, yield a smaller SIC in dependence of the 5d weight. Simultaneously, this parameter determines the 4f occupancy. Our self-consistent SIC-LDA calculation shows that the correlation between the MO level position and the 4f occupancy is consistent with experiment if only one of the six 4f states is treated in this way. If the MO level reaches the bottom of the conduction band a reconstruction of the electronic structure should take place. (orig.)

[en] The magnetic field profiles near the surface of a Sm₁Ba₂Cu₃O_7-δ coated conductor(CC-tape) under magnetic field and current that were applied simultaneously with phase differences φs were measured using scanning Hall probe method. Measurements were carried out along the elliptic load lines with φ= 90 degrees and 45 degrees for some B_peak, I_peak values. From the measured field profiles, sheet current density J(x, B_a1, I_a1) and magnetic flux density B₀(x, B_a, I_a) profiles in the CC-tape were calculated. Using these J(x, B_a, I_a) and B₀(x, B_a, I_a) profiles, we estimated the hysteresis energy loss Q in the CC-tape. The estimated Qs, together with our previous results for φ=0 degrees from [9], were compared with theoretical values based on Brandt's calculation.

[en] A model calculation is presented, based on the Falicov-Kimball model for metal-insulator transitions, which shows that for a mixed-valence solid with a surface, the average valence of the atoms at the surface may be substantially different from that in the bulk. The effect, which has been calculated only for T = 0 and neglecting hybridization, is due to the different local density of itinerant states at the surface and bulk atoms. Surface states contribute to the valence difference but are not solely responsible for it. (author)

No abstract available

[en] XPS 4f spectra of rare-earth hexaborides are presented. Unusually large 4f lifetime broadening was detected throughout the whole series. Its origin is discussed. Of special interest is SmB₆, a well-known mixed-valence compound. The Sm 4f spectrum yields several quantitative conclusions regarding the mixed configuration ground state

No abstract available