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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Multiphase magnetism in Yb 2 Ti 2 O 7

We use neutron scattering to show that ferromagnetism and antiferromagnetism coexist in the low T state of the pyrochlore quantum magnet Yb 2 Ti 2 O 7 . While magnetic Bragg peaks evidence long-range static ferromagnetic order, inelastic scattering shows that short-range correlated antiferromagnetism is also present. Small-angle neutron scattering provides direct evidence for mesoscale magnetic structure that we associate with metastable antiferromagnetism. Classical Monte Carlo simulations based on exchange interactions inferred from ⟨ 111 ⟩ -oriented high-field spin wave measurements confirm that antiferromagnetism is metastable within the otherwise ferromagnetic ground state. The apparent lack of coherent spin wave excitations and strong sensitivity to quenched disorder characterizing Yb 2 Ti 2 O 7 is a consequence of this multiphase magnetism.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Nuclear deformation as a source of the nonlinearity of the King plot in the Yb + ion

We perform atomic relativistic many-body calculations of the field isotope shifts and calculations of corresponding nuclear parameters for all stable even-even isotopes of the Yb + ion. We demonstrate that if we take nuclear parameters of the Yb isotopes from a range of the state of the art nuclear models, which all predict strong quadrupole nuclear deformation, and then calculate nonlinearity of the King plot caused by the difference in the deformation in different isotopes, the result is consistent with the nonlinearity observed in the experiment. In conclusion, the changes of nuclear rms radius between isotopes extracted from experiment are consistent with those obtained in the nuclear calculations.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2021

Czochralski growth and characterization of the multicomponent garnet (Lu 1/4 Yb 1/4 Y 1/4 Gd 1/4 ) 3 Al 5 O 12

This work demonstrates the potential for practical scalable growth of complex garnets and evaluates the implications of a multicomponent composition in the optical quality and elemental distribution of a Czochralski-grown crystal. Furthermore, our experimental approach was designed to elucidate the relation between a complex garnet composition ( Lu 1 / 4 Yb 1 / 4 Y 1 / 4 Gd 1 / 4 ) 3 Al 5 O 12 , crystal growth parameters, crystal structural, and elemental homogeneity. Our hypothesis is that combining multiple rare earths (REs) that will fractionally occupy the dodecahedral site in the aluminum garnet structure will result in a stable, single garnet compound that can be grown by the Czochralski method. Single-crystal and powder x-ray diffraction indicated a single garnet phase with an increasing unit cell volume from seed to tail. In addition, we propose that the pattern of elemental segregation will be based on the deviation of the ionic radius of each constituent RE from the average RE ionic radius of the multicomponent garnet. Electron probe microanalysis revealed that ions that are smaller than that average ( Lu 3 + and Yb 3 + ) are preferentially incorporated in the crystal, while elements that are larger than that average ( Gd 3 + ) are rejected. The ionic radius of Y 3 + is close to that average and yttrium segregation was minimal. The concentrations of the four REs are closer to stoichiometric on the tail end of the boule. Scanning electron microscopy and energy-dispersive x-ray spectroscopy analysis reveal Gd-rich inclusions with eutectic microstructures in the tail end of the boule.

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

Defect Structure in Quantum-Cutting Yb3+-Doped CsPbCl3 Perovskites Probed by X-Ray Absorption and Atomic Pair Distribution Function Analysis

Ytterbium-doping in all-inorganic lead-halide perovskites (CsPb(Cl1-xBrx)3) generates novel properties including quantum cutting and narrow line emission, making these materials attractive spectral down-converters for solar photovoltaics. The relationship between this optical efficiency and the defect structure(s) associated with Yb3+ dopants within perovskites is not well understood. Various charge-neutral doping motifs have previously been proposed and studied computationally, including clusters involving two substitutional Yb3+ ions charge-compensated by a single local Pb2+ vacancy. Near-band-edge defect states associated with such motifs are believed to play an important mechanistic role in quantum cutting itself. Here, we report the results of X-ray absorption and X-ray total-scattering measurements on ytterbium-doped CsPbCl3. XANES shows that the dopant oxidation state is exclusively Yb3+, and a combination of Yb L3 and Pb L3 EXAFS shows that this Yb3+ substitutes exclusively at Pb2+ sites, where it adopts a pseudo-octahedral [YbCl6]3- coordination environment. Shell-by-shell fits to the data show a short Yb-Cl bond distance of 2.58 Å compared to the Pb-Cl bond distance of 2.83 Å. We confirm this finding by X-ray pair distribution function analysis, which also shows evidence of additional Pb2+ vacancy formation induced by Yb3+ doping. We evaluate whether this is the primary mechanism of charge compensation using simulated EXAFS and pair distribution function data for several computed defect structures. Together, these results resolve the local dopant structures and charge-compensation mechanisms in lanthanide-doped all-inorganic lead-halide perovskites, and, as such, significantly advance the understanding of structure-function relationships in this important class of materials.

Kluherz, Kyle (ORCID:0000000279865167)↗
DOE OSTI2020

Laser induced damage in coatings for cryogenic Yb:YAG active mirror amplifiers

We report results of a study of the laser induced damage threshold (LIDT) behavior of ion beam sputtered H f O 2 / S i O 2 multilayer coatings on Yb:YAG using 1-on-1 and N-on-1 test protocols. The tests were conducted at ambient, vacuum, and cryogenic conditions using 280 ps pulses at λ <#comment/> = 1030 n m . The 1-on-1 LIDT of antireflection (AR) stacks is found to be only slightly reduced under vacuum and cryogenic conditions, while that of high reflectivity (HR) stacks is insensitive to environmental conditions within the uncertainty of the measurements. Cryogenic N-on-1 tests show the LIDT of the HR coating is almost the same as in the 1-on-1 tests. Conversely, the cryogenic N-on-1 test of the AR coating shows damage at ∼ <#comment/> 13 J / c m 2 , a fluence lower than the 20.4 J / c m 2 of 1-on-1 tests. The AR damage behavior is found to be affected by imperfections at the Yb:YAG surface. These findings show that high surface quality is required to increase energy extraction from active mirror laser amplifiers.

Wang, Hanchen↗
DOE OSTI2023

1.2-kW all-fiber Yb-doped multicore fiber amplifier

Here we have demonstrated a record-high 1.2 kW, all-fiber multicore amplifier using a six-core single-mode Yb-doped fiber and a multicore pump-signal combiner (PSC). The output power is limited by the pump power of 1.9 kW. We have developed double-clad six-core fibers and PSCs for this demonstration. Each of the six Yb-doped cores has a 17-µm mode-field diameter (MFD) with a trench index profile and is capable of kW-class operation. The potential power scaling to the 10-kW level in a single amplifier with high brightness should be feasible with advanced thermal management and coherent beam combination.

42 ENGINEERING↗
DOE OSTI2020

Low-Energy Electron Elastic Total Cross Sections for Ho, Er, Tm, Yb, Lu, and Hf Atoms

The robust Regge-pole methodology wherein is fully embedded the essential electron-electron correlation effects and the vital core polarization interaction has been used to explore negative ion formation in the large lanthanide Ho, Er, Tm, Yb, Lu, and Hf atoms through the electron elastic total cross sections (TCSs) calculations. These TCSs are characterized generally by dramatically sharp resonances manifesting ground, metastable, and excited negative ion formation during the collisions, Ramsauer-Townsend minima, and shape resonances. The novelty and generality of the Regge-pole approach is in the extraction of the negative ion binding energies (BEs) of complex heavy systems from the calculated electron TCSs. The extracted anionic BEs from the ground state TCSs for Ho, Er, Tm, Yb, Lu, and Hf atoms are 3.51 eV, 3.53 eV, 3.36 eV, 3.49 eV, 4.09 eV and 1.68 eV, respectively. The TCSs are presented and the extracted from the ground; metastable and excited anionic states BEs are compared with the available measured and/or calculated electron affinities. We conclude with a remark on the existing inconsistencies in the meaning of the electron affinity among the various measurements and/or calculations in the investigated atoms and make a recommendation to resolve the ambiguity.

Felfli, Zineb↗
DOE OSTI2020

Crystal Structure and Magnetic Properties of the Breathing Kagome Ising Antiferromagnet Yb 3 Ni 11 Ge 4.63

We have investigated magnetic properties of the rare-earth based intermetallic compound Yb 3 Ni 11 Ge 4.63 (YNG), where Yb 3+ ions form a breathing-kagome lattice. Single-site 4f electron wavefunctions of the ground-state doublet are deduced from magnetization and heat capacity measurements. The Weiss temperatures are quite anisotropic as Θ a = -0.01(2) K (H ∥ a) and Θ c = -0.67(2) K (H ∥ c), indicating Ising-like spin–spin interactions dominating in this compound. Low-temperature neutron diffraction confirms absence of magnetic Bragg peaks down to 0.05 K, whereas enhancement of broad peaks below 0.8 K was observed, a signature of short-range spin correlations. Furthermore, competing interactions on the breathing-kagome lattice would suppress a magnetic long-range order in YNG.

36 MATERIALS SCIENCE↗
NASA NTRS1994

Evaluation of reformulated thermal control coatings in a simulated space environment. Part 1: YB-71

The Air Force Space and Missile Systems Center and Wright Laboratory Materials Directorate (WL/ML) have sponsored and effort to effort to reformulate and qualify Illinois Institute of Technology Research Institute (IITRI) spacecraft thermal control coatings. S13G/LO-1, Z93, and YB-71 coatings were reformulated because the potassium silicate binder, Sylvania PS-7, used in the coatings is no longer manufactured. Coatings utilizing the binder's replacement candidate, Kasil 2130, manufactured by The Philadelphia Quartz (PQ) Corporation, Baltimore, Maryland, and undergoing testing at the Materials Directorate's Space Combined Effects Primary Test and Research Equipment (SCEPTRE) Facility operated by the University of Dayton Research Institute (UDRI). The simulated space environment consists of combined ultraviolet (UV) and electron exposure with in site specimen reflectance measurements. A brief description of the effort at IITRI, results and discussion from testing the reformulated YB-71 coating in SCEPTRE, and plans for further testing of reformulated Z93 and S13G/LO-1 are presented.

Cerbus, Clifford A.↗
NASA NTRS2001

Yb fiber laser pumped mid-IR source based on difference frequency generation and its application to ammonia detection

A Yb fiber laser pumped cw narrow-linewidth tunable mid-IR source based on a difference frequency generation (DFG) in a periodically poled LiNbO3 (PPLN) crystal for trace gas detection was demonstrated. A high power Yb fiber laser and a distributed feedback (DFB) laser diode were used as DFG pump sources. This source generated mid-IR at 3 microns with a powers of ~2.5 microW and a spectral linewidth of less than 30 MHz. A frequency tuning range of 300 GHz (10 cm-1) was obtained by varying the current and temperature of the DFB laser diode. A high-resolution NH3 absorption Doppler-broadened spectrum at 3295.4 cm-1 (3.0345 microns) was obtained at a cell pressure of 27 Pa from which a detection sensitivity of 24 ppm m was estimated.

NASA Discipline Environmental Health↗
DOE OSTI2020

Materials Data on Yb(ZnAs)2 by Materials Project

YbZn2As2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Yb2+ is bonded to six equivalent As3- atoms to form YbAs6 octahedra that share corners with twelve equivalent ZnAs4 tetrahedra, edges with six equivalent YbAs6 octahedra, and edges with six equivalent ZnAs4 tetrahedra. All Yb–As bond lengths are 3.00 Å. Zn2+ is bonded to four equivalent As3- atoms to form ZnAs4 tetrahedra that share corners with six equivalent YbAs6 octahedra, corners with six equivalent ZnAs4 tetrahedra, edges with three equivalent YbAs6 octahedra, and edges with three equivalent ZnAs4 tetrahedra. The corner-sharing octahedra tilt angles range from 18–54°. There are three shorter (2.54 Å) and one longer (2.64 Å) Zn–As bond lengths. As3- is bonded to three equivalent Yb2+ and four equivalent Zn2+ atoms to form a mixture of distorted edge and corner-sharing AsYb3Zn4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(AlSi)2 by Materials Project

YbAl2Si2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Yb2+ is bonded to six equivalent Si4- atoms to form YbSi6 octahedra that share corners with twelve equivalent AlSi4 tetrahedra, edges with six equivalent YbSi6 octahedra, and edges with six equivalent AlSi4 tetrahedra. All Yb–Si bond lengths are 3.02 Å. Al3+ is bonded to four equivalent Si4- atoms to form AlSi4 tetrahedra that share corners with six equivalent YbSi6 octahedra, corners with six equivalent AlSi4 tetrahedra, edges with three equivalent YbSi6 octahedra, and edges with three equivalent AlSi4 tetrahedra. The corner-sharing octahedra tilt angles range from 20–52°. There are three shorter (2.51 Å) and one longer (2.61 Å) Al–Si bond lengths. Si4- is bonded to three equivalent Yb2+ and four equivalent Al3+ atoms to form a mixture of distorted edge and corner-sharing SiYb3Al4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(SiRh)2 by Materials Project

YbRh2Si2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Yb2+ is bonded in a distorted body-centered cubic geometry to eight equivalent Si4- atoms. All Yb–Si bond lengths are 3.16 Å. Rh3+ is bonded to four equivalent Si4- atoms to form a mixture of corner and edge-sharing RhSi4 tetrahedra. All Rh–Si bond lengths are 2.39 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent Yb2+, four equivalent Rh3+, and one Si4- atom. The Si–Si bond length is 2.49 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(SiAg)2 by Materials Project

YbAg2Si2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Yb3+ is bonded to eight equivalent Si4- atoms to form YbSi8 hexagonal bipyramids that share corners with sixteen equivalent AgSi4 tetrahedra, edges with four equivalent YbSi8 hexagonal bipyramids, edges with eight equivalent AgSi4 tetrahedra, and faces with four equivalent YbSi8 hexagonal bipyramids. All Yb–Si bond lengths are 3.23 Å. Ag+2.50+ is bonded to four equivalent Si4- atoms to form AgSi4 tetrahedra that share corners with eight equivalent YbSi8 hexagonal bipyramids, corners with four equivalent AgSi4 tetrahedra, edges with four equivalent YbSi8 hexagonal bipyramids, and edges with four equivalent AgSi4 tetrahedra. All Ag–Si bond lengths are 2.60 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent Yb3+, four equivalent Ag+2.50+, and one Si4- atom. The Si–Si bond length is 2.28 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(FeP3)4 by Materials Project

YbFe4P12 crystallizes in the cubic Im-3 space group. The structure is three-dimensional. Yb2+ is bonded to twelve equivalent P1- atoms to form YbP12 cuboctahedra that share faces with eight equivalent FeP6 octahedra. All Yb–P bond lengths are 2.99 Å. Fe+2.50+ is bonded to six equivalent P1- atoms to form FeP6 octahedra that share corners with six equivalent FeP6 octahedra and faces with two equivalent YbP12 cuboctahedra. The corner-sharing octahedral tilt angles are 60°. All Fe–P bond lengths are 2.24 Å. P1- is bonded in a 2-coordinate geometry to one Yb2+, two equivalent Fe+2.50+, and two equivalent P1- atoms. There are one shorter (2.28 Å) and one longer (2.34 Å) P–P bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(MnSi)2 by Materials Project

YbMn2Si2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Yb3+ is bonded in a body-centered cubic geometry to eight equivalent Si4- atoms. All Yb–Si bond lengths are 3.06 Å. Mn+2.50+ is bonded to four equivalent Si4- atoms to form a mixture of corner and edge-sharing MnSi4 tetrahedra. All Mn–Si bond lengths are 2.36 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent Yb3+, four equivalent Mn+2.50+, and one Si4- atom. The Si–Si bond length is 2.55 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(Ni2P)2 by Materials Project

YbNi4P2 crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. Yb2+ is bonded to six equivalent P3- atoms to form a mixture of corner and edge-sharing YbP6 octahedra. The corner-sharing octahedral tilt angles are 38°. There are two shorter (2.78 Å) and four longer (2.85 Å) Yb–P bond lengths. Ni1+ is bonded in a trigonal planar geometry to three equivalent P3- atoms. There are two shorter (2.28 Å) and one longer (2.30 Å) Ni–P bond lengths. P3- is bonded in a 9-coordinate geometry to three equivalent Yb2+ and six equivalent Ni1+ atoms.

36 MATERIALS SCIENCE↗