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8 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on EuCu(WO4)2 by Materials Project

EuCu(WO4)2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. Eu3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Eu–O bond distances ranging from 2.41–2.75 Å. There are two inequivalent W6+ sites. In the first W6+ site, W6+ is bonded in a distorted octahedral geometry to six O2- atoms. There are a spread of W–O bond distances ranging from 1.82–2.17 Å. In the second W6+ site, W6+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of W–O bond distances ranging from 1.78–2.36 Å. Cu1+ is bonded in a 3-coordinate geometry to three O2- atoms. There are a spread of Cu–O bond distances ranging from 1.88–1.99 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Eu3+, one W6+, and one Cu1+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Eu3+ and one W6+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Eu3+ and two W6+ atoms. In the fourth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Eu3+ and one W6+ atom. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Eu3+ and one W6+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to three W6+ and one Cu1+ atom. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to one Eu3+, one W6+, and one Cu1+ atom. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to one Eu3+ and two W6+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Intermediate-valence state of the Sm and Eu in SmB 6 and EuCu 2 Si 2 : neutron spectroscopy data and analysis

For this study, magnetic neutron scattering data for Sm (SmB 6 , Sm(Y)S) and Eu (EuCu 2 Si 2 - x Ge x ) intermediate-valence compounds have been analysed in terms of a generalized model of the intermediate-radius exciton. Special attention is paid to the correlation between the average ion's valence and parameters of the low-energy excitation in the neutron spectra, such as the resonance mode, including its magnetic form factor. Along with specific features of the formation of the intermediate-valence state for Sm and Eu ions, common physical mechanisms have been revealed for systems based on these elements from the middle of the rare-earth series. A consistent description of the existing experimental data has been obtained by using the concept of a loosely bound hole for the Eu f-electron shell in the intermediate-valence state, in analogy with the previously established loosely bound electron model for the Sm ion.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Materials Data on EuCu by Materials Project

CuEu is Tetraauricupride structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Eu is bonded in a body-centered cubic geometry to eight equivalent Cu atoms. All Eu–Cu bond lengths are 3.14 Å. Cu is bonded in a body-centered cubic geometry to eight equivalent Eu atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on EuCu by Materials Project

CuEu crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Eu is bonded in a 7-coordinate geometry to seven equivalent Cu atoms. There are a spread of Eu–Cu bond distances ranging from 3.04–3.34 Å. Cu is bonded in a 9-coordinate geometry to seven equivalent Eu and two equivalent Cu atoms. Both Cu–Cu bond lengths are 2.57 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on EuCu(MoO4)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2021

Dynamic fingerprint of fractionalized excitations in single-crystalline Cu3Zn(OH)6FBr

Abstract Beyond the absence of long-range magnetic orders, the most prominent feature of the elusive quantum spin liquid (QSL) state is the existence of fractionalized spin excitations, i.e., spinons. When the system orders, the spin-wave excitation appears as the bound state of the spinon-antispinon pair. Although scarcely reported, a direct comparison between similar compounds illustrates the evolution from spinon to magnon. Here, we perform the Raman scattering on single crystals of two quantum kagome antiferromagnets, of which one is the kagome QSL candidate Cu 3 Zn(OH) 6 FBr, and another is an antiferromagnetically ordered compound EuCu 3 (OH) 6 Cl 3 . In Cu 3 Zn(OH) 6 FBr, we identify a unique one spinon-antispinon pair component in the E 2g magnetic Raman continuum, providing strong evidence for deconfined spinon excitations. In contrast, a sharp magnon peak emerges from the one-pair spinon continuum in the E g magnetic Raman response once EuCu 3 (OH) 6 Cl 3 undergoes the antiferromagnetic order transition. From the comparative Raman studies, we can regard the magnon mode as the spinon-antispinon bound state, and the spinon confinement drives the magnetic ordering.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Investigating the Role of Vacancies on the Thermoelectric Properties of EuCuSb‐Eu 2 ZnSb 2 Alloys

Abstract AMX compounds with the ZrBeSi structure tolerate a vacancy concentration of up to 50 % on the M ‐site in the planar MX ‐layers. Here, we investigate the impact of vacancies on the thermal and electronic properties across the full EuCu 1− x Zn 0.5 x Sb solid solution. The transition from a fully‐occupied honeycomb layer (EuCuSb) to one with a quarter of the atoms missing (EuZn 0.5 Sb) leads to non‐linear bond expansion in the honeycomb layer, increasing atomic displacement parameters on the M and Sb‐sites, and significant lattice softening. This, combined with a rapid increase in point defect scattering, causes the lattice thermal conductivity to decrease from 3 to 0.5 W mK −1 at 300 K. The effect of vacancies on the electronic properties is more nuanced; we see a small increase in effective mass, large increase in band gap, and decrease in carrier concentration. Ultimately, the maximum zT increases from 0.09 to 0.7 as we go from EuCuSb to EuZn 0.5 Sb.

Chanakian, Sevan↗
DOE OSTI2023

Investigating the Role of Vacancies on the Thermoelectric Properties of EuCuSb‐Eu 2 ZnSb 2 Alloys

Abstract AMX compounds with the ZrBeSi structure tolerate a vacancy concentration of up to 50 % on the M ‐site in the planar MX ‐layers. Here, we investigate the impact of vacancies on the thermal and electronic properties across the full EuCu 1− x Zn 0.5 x Sb solid solution. The transition from a fully‐occupied honeycomb layer (EuCuSb) to one with a quarter of the atoms missing (EuZn 0.5 Sb) leads to non‐linear bond expansion in the honeycomb layer, increasing atomic displacement parameters on the M and Sb‐sites, and significant lattice softening. This, combined with a rapid increase in point defect scattering, causes the lattice thermal conductivity to decrease from 3 to 0.5 W mK −1 at 300 K. The effect of vacancies on the electronic properties is more nuanced; we see a small increase in effective mass, large increase in band gap, and decrease in carrier concentration. Ultimately, the maximum zT increases from 0.09 to 0.7 as we go from EuCuSb to EuZn 0.5 Sb.

36 MATERIALS SCIENCE↗