Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Gd-Yb”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Synthesis and magnetic properties of the Shastry-Sutherland family R 2 Be 2 SiO 7 ( R = Nd , Sm , Gd-Yb )

Compounds forming the quasi-two-dimensional Shastry-Sutherland lattice (SSL) have attracted significant experimental and theoretical attention in the field of frustrated magnetism. This is primarily due to their realization of an exactly soluble J 1 –J 2 orthogonal dimer model capable of hosting magnetic order, dimer singlet, and plaquette singlet phases in zero applied field and their complex magnetic phase diagrams with fractional magnetization plateaus and possible superfluid and supersolid phases found between the plateau states. The discovery and characterization of SSL compounds based on rare-earth magnetic ions provide a direct route to study the stability and properties of these exotic magnetic phases in systems with a variety of different magnetic anisotropies. In this paper, we discuss the synthesis and magnetic characterization of polycrystalline samples of the R 2 ⁢Be 2 ⁢SiO 7 family, where R=Nd, Sm, and Gd-Yb. All family members crystallize in the space group $P\bar{⁢4}⁢2_1⁢m$ (113) and show no signs of long-range magnetic order above 2 K, except for R=Tb which orders antiferromagnetically at 2.6 K.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Unconventional magnetic order emerging from competing energy scales in the new R Rh 3 Si 7 intermetallics ( R = Gd-Yb)

The competition between Ruderman-Kittel-Kasuya-Yosida (RKKY), crystal electric field (CEF), and Kondo energy scales has recently emerged at the heart of complex magnetism in several Ce- or Yb-based intermetallics. Hard axis magnetic order has been observed in a handful of these compounds, independent of the crystal symmetry, size of the ordered moment, or the relative scale of the Kondo and magnetic ordering temperatures. This raises the question of the role of each energy scale in driving the ground state properties. In focusing on a single class of compounds, the rhombohedral RRh 3 Si 7 , we compare the anisotropy and magnetic ground states in members of this series with only RKKY interactions (R = Gd), or RKKY and CEF effects (R = Tb-Tm), with the behavior of the R = Yb compound, where all three energy scales (RKKY, CEF, Kondo) are at play. Moreover, we extend the comparison to two other isostructural Kondo systems YbIr 3 Si 7 and YbIr 3 Ge 7 , where hard axis magnetic order is also observed. The non-Kondo compounds RRh 3 Si 7 (R = Tb-Tm) lack the complexity of magnetic order along the hard CEF axis, pointing to the dominant role of the Kondo effect in driving this magnetic order. Furthermore, the CEF-RKKY competition is still responsible for complex magnetic ground states, and it appears that the electronic and magnetic degrees of freedom are entangled in all magnetic members of this series of compounds.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Homologous Alkali Metal Copper Rare-Earth Chalcogenides A 2 Cu 2 n Ln 4 Q 7+ n ( n = 1, 2, 3)

Twenty-seven new members of the A 2 Cu 2n Ln 4 Q 7+n (A = Cs, Rb; Ln = La-Nd, Sm, Gd-Yb; Q = S, Se) homologous series were synthesized in one of three structural types (indicated by n = 1, 2, 3). All the compounds contained 3D frameworks with alkali-metal-containing tunnels. For each increment in n, one Cu 2 Q was added, which was incorporated into the framework as an edge-sharing tetrahedron by replacing a square planar chalcogenide site. High-throughput DFT calculations predicted many of the phases to be thermodynamically stable. These predictions were compared with the synthesis results for the phases formed in each composition space. In the syntheses, heavier lanthanides showed a preference to start forming the n = 3 ACu 3 Ln 2 Q 5 , which is consistent with the predictions. RbCuNd 2 Se 4 and RbCuTb 2 Se 4 were found to be thermally stable under vacuum at temperatures up to 1000 °C. Optical measurements revealed band gaps of 1.55(5) and 1.62(5) eV for CsCuCe 2 Se 4 and RbCuTb 2 Se 4 , respectively, and a work function of 4.83(5) eV for CsCuPr 2 Se 4 . Additionally, some n = 3 ACu 3 Ln 2 Qs compounds exhibit a negative phonon mode because of a copper atom coordination, which may distort to a trigonal planar geometry at sufficiently low temperatures. The dynamic instabilities and the predicted distortion in the copper tetrahedra for the n = 3 ACu 3 Ln 2 Q 5 compounds were found to have a linear relationship with the atomic number of the lanthanides and the electronegativity of the lanthanides. In conclusion, the A 2 Cu 2 n Ln 4 Q 7+n compounds can potentially find application as high-temperature thermoelectric materials and other semiconductors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1974

Minor and trace element distribution in melilite and pyroxene from the Allende meteorite

Melilite and pyroxene were separated from a coarsely crystalline chondrule in the Allende meteorite and analyzed by microprobe and spark source mass spectrometer techniques. Elemental abundances in the bulk chondrule are consistent with a mixture of equal amounts of the two minerals, as observed microscopically. The lanthanide distributions are markedly different in the two minerals; relative to chondrite abundances, melilite shows progressive depletion of the lanthanides La-Sm, a positive Eu anomaly, and relatively constant abundances of the heavier lanthanides (Gd-Yb, and Y) whereas pyroxene shows progressive enrichment towards the heavier lanthanides, on which is superimposed a negative Eu anomaly. Both minerals, and the bulk chondrule, show unusual concentrations of the platinum metals, but the crystallographic site or sites of these metals remains to be determined.

Mason, B.↗
DOE OSTI2020

Materials Data on YbGd3 by Materials Project

YbGd3 is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Yb is bonded to twelve Gd atoms to form YbGd12 cuboctahedra that share corners with six equivalent YbGd12 cuboctahedra, corners with twelve GdYb4Gd8 cuboctahedra, edges with eighteen GdYb4Gd8 cuboctahedra, faces with eight equivalent YbGd12 cuboctahedra, and faces with twelve GdYb4Gd8 cuboctahedra. There are six shorter (3.35 Å) and six longer (3.44 Å) Yb–Gd bond lengths. There are three inequivalent Gd sites. In the first Gd site, Gd is bonded to four equivalent Yb and eight Gd atoms to form GdYb4Gd8 cuboctahedra that share corners with four equivalent YbGd12 cuboctahedra, corners with fourteen GdYb4Gd8 cuboctahedra, edges with six equivalent YbGd12 cuboctahedra, edges with twelve GdYb4Gd8 cuboctahedra, faces with four equivalent YbGd12 cuboctahedra, and faces with sixteen GdYb4Gd8 cuboctahedra. There are a spread of Gd–Gd bond distances ranging from 3.32–3.49 Å. In the second Gd site, Gd is bonded to four equivalent Yb and eight Gd atoms to form GdYb4Gd8 cuboctahedra that share corners with four equivalent YbGd12 cuboctahedra, corners with fourteen GdYb4Gd8 cuboctahedra, edges with six equivalent YbGd12 cuboctahedra, edges with twelve GdYb4Gd8 cuboctahedra, faces with four equivalent YbGd12 cuboctahedra, and faces with sixteen GdYb4Gd8 cuboctahedra. There are a spread of Gd–Gd bond distances ranging from 3.32–3.49 Å. In the third Gd site, Gd is bonded to four equivalent Yb and eight Gd atoms to form GdYb4Gd8 cuboctahedra that share corners with four equivalent YbGd12 cuboctahedra, corners with fourteen GdYb4Gd8 cuboctahedra, edges with six equivalent YbGd12 cuboctahedra, edges with twelve GdYb4Gd8 cuboctahedra, faces with four equivalent YbGd12 cuboctahedra, and faces with sixteen GdYb4Gd8 cuboctahedra.

36 MATERIALS SCIENCE↗