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All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Ferroelectricity and superconductivity in strained Eu x Sr 1 – x TiO 3 films

The superconducting transition of SrTiO 3 can be influenced by tuning its ferroelectric transition, but the underlying reasons remain poorly understood. Here, we investigate compressively strained, Sm-doped films of Eu x Sr 1-x TiO 3 that were grown by molecular beam epitaxy to determine the effect of alloying with Eu on both superconductivity and ferroelectricity, both of which are present in strained SrTiO 3 films. Remarkably, superconductivity survives up to x = 0.14. Films at the lowest alloy concentration studied here, x = 0.09, exhibit no suppression of their superconducting transition temperature, but a strong reduction of the upper critical field (H c2 ), compared to non-alloyed, strained SrTiO 3 films. In addition, these films lack the sharp ferroelectric transition that appears in films without Eu in second harmonic generation measurements. Here, we postulate that Eu-alloying causes a crossover from a globally ordered ferroelectric state to one with only short-range polar order. We discuss the connection between the loss of global polar order and the change in the superconducting properties.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Decay spectroscopy of 160 Eu: Quasiparticle configurations of excited states and structure of K π = 4 + bandheads in 160 Gd

Background: Detailed spectroscopy of neutron-rich, heavy, deformed nuclei is of broad interest for nuclear astrophysics and nuclear structure. Nuclei in the r-process path and following freeze-out region impact the resulting r-process abundance distribution, and the structure of nuclei midshell in both proton and neutron number helps to understand the evolution of subshell gaps and large deformation in these nuclei. Purpose: We aim to improve the understanding of the nuclear structure of 160 Gd, specifically the K π = 4 + bands, as well as study the β decay of 160 Eu into 160 Gd. Methods: High-statistics decay spectroscopy of 160 Gd resulting from the β-decay of 160 Eu was collected using the GRIFFIN spectrometer at the TRIUMF-ISAC facility. Results: Two new excited states and ten new transitions were observed in 160 Gd. The β-decaying half-lives of the low- and high-spin isomers in 160 Eu were determined, and the low-spin state's half-life was measured to be t 1/2 = 26.0 (8) s, ≈ 16% shorter than previous measurements. Lifetimes of the two K π = 4 + bandheads in 160 Gd were measured for the first time, as well as γ – γ angular correlations and mixing ratios of intense transitions out of those bandheads. Conclusions: Lifetimes and mixing ratios suggest that the hexadecapole phonon model of the K π = 4 + bandheads in 160 Gd is preferred over a simple two-state strong mixing scenario, although further theoretical calculations are needed to fully understand these states. Additionally, the 1999.0-keV state in 160 Gd heavily populated in β decay is shown to have positive parity, which raises questions regarding the structure of the high-spin β-decaying state in 160 Eu.

150 ≤ A ≤ 189↗
DOE OSTI2021

Antiferro- and metamagnetism in the S = 7 / 2 hollandite analog Eu Ga 2 Sb 2

Recent work analyzing the impact of nonsymmorphic symmetries on electronic states has given rise to the discovery of multiple types of topological matter. Here we report the single-crystal synthesis and magnetic properties of Eu Ga 2 Sb 2 , a Eu-based antiferromagnet structurally consisting of pseudo-1D chains of Eu ions related by a nonsymmorphic glide plane. Here we find the onset of antiferromagnetic order at T N = 8K. Above T N the magnetic susceptibility is isotropic. Curie-Weiss analysis suggests competing ferromagnetic and antiferromagnetic interactions, with p eff = 8.1 μ B as expected for 4f 7 J = S = 7/2 Eu 2+ ions. Below T N and at low applied magnetic fields, an anisotropy develops linearly, reaching χ ⊥ /χ ∥ = 6 at T = 2K. There is concomitant metamagnetic behavior along χ ∥ , with a magnetic field of μ 0 H ≈ 0.5 T sufficient to suppress the anisotropy. Independent of crystal orientation, there is a continuous evolution to a field-polarized paramagnetic state with M = 7μ B /Eu 2+ at μ 0 H = 2 T as T → 0 K. Specific-heat measurements show a recovered magnetic entropy of ΔS mag ≈ 16.4 Jmol –1 K –1 from T ~ 0 K to T = T N , close to the expected value of R ln(8) for an S = 7/2 ion, indicating negligible low-dimensional spin fluctuations above T N . We find no evidence of unusual behaviors arising either from the dimensionality or the presence of the nonsymmorphic symmetries.

1-dimensional spin chains↗
DOE OSTI2023

Structural transition and anisotropic magnetism in disordered Zintl phase Eu 7 Ga 6 Sb 8

Single crystals of the Zintl compound Eu 7 Ga 6 Sb 8 were synthesized using a Ga-Sb flux. We report the temperature (T) and magnetic field (H) dependence of the magnetic susceptibility (χ), magnetization (M), resistivity (ρ), specific heat (C), and thermal expansion (α). We also report high-resolution powder x-ray diffraction data that support a structural phase transition with accompanying signatures seen in C(T), ρ(T), and α(T). We find Eu 7 Ga 6 Sb 8 exhibits antiferromagnetic ordering at T N1 = 9.0 K from anomalies seen in χ(T), C(T), and α(T), as well as a potential reorientation of Eu 2+ spins at T N2 = 7.5 K and T N3 = 7.2 K. In conclusion, density functional theory calculations predict Eu 7 Ga 6 Sb 8 to be semiconducting; however, electrical resistivity measurements show bad-metal behavior that indicates the presence of disorder.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Superconducting Nd 1- x Eu x NiO 2 thin films using in situ synthesis

We report on superconductivity in Nd 1-x Eu x NiO 2 using Eu as a 4f dopant of the parent NdNiO 2 infinite-layer compound. We use an all–in situ molecular beam epitaxy reduction process to achieve the superconducting phase, providing an alternate method to the ex situ CaH 2 reduction process to induce superconductivity in the infinite-layer nickelates. The Nd 1-x Eu x NiO 2 samples exhibit a step-terrace structure on their surfaces, have a T c onset of 21 K at x = 0.25, and have a large upper critical field that may be related to Eu 4f doping.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Fluorescence-Based Aqueous Phosphate Sensing Using Eu(cpboda)(DMF) 2

Fluorescence-based phosphate sensing using phosphate-sensitive phosphors is a promising approach for in situ monitoring of phosphate pollution in waterways and reservoirs. To date, the most sensitive phosphor developed for this purpose is Tb(cpboda)(DMF) 2 , where cpboda = (3,3'-((5-Carboxy-1,3-phenylene)bis(oxy))dibenzoic acid). In this study, we further improve this sensitivity by replacing the Tb 3+ ions with Eu 3+ ions to make Eu(cpboda)(DMF) 2 and find concentration-independent phosphate-sensitivity of 1570 ± 120, which is ≈8× more sensitive than the Tb-version. This improvement is attributed to Eu 3+ having a hypersensitive transition, while Tb 3+ does not. Additionally, we characterize the phosphor’s optical properties, photodegradation, and water solubility. We find that the phosphor presents challenges with regards to both photodegradation and solubility, as it is found to be poorly soluble in water and is quickly photodegraded under UV radiation <360 nm. However, these obstacles can, in theory, be overcome with the use of direct excitation of the Eu 3+ ions at 394 nm and careful design of an analysis instrument to reduce concentration variations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on Eu(AlGe)2 by Materials Project

EuAl2Ge2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Eu is bonded to six equivalent Ge atoms to form EuGe6 octahedra that share corners with twelve equivalent AlGe4 tetrahedra, edges with six equivalent EuGe6 octahedra, and edges with six equivalent AlGe4 tetrahedra. All Eu–Ge bond lengths are 3.10 Å. Al is bonded to four equivalent Ge atoms to form AlGe4 tetrahedra that share corners with six equivalent EuGe6 octahedra, corners with six equivalent AlGe4 tetrahedra, edges with three equivalent EuGe6 octahedra, and edges with three equivalent AlGe4 tetrahedra. The corner-sharing octahedra tilt angles range from 20–52°. There are three shorter (2.57 Å) and one longer (2.63 Å) Al–Ge bond lengths. Ge is bonded to three equivalent Eu and four equivalent Al atoms to form a mixture of distorted corner and edge-sharing GeEu3Al4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(AlCl4)2 by Materials Project

Eu(AlCl4)2 crystallizes in the monoclinic P2/c space group. The structure is two-dimensional and consists of one Eu(AlCl4)2 sheet oriented in the (1, 0, 0) direction. Eu2+ is bonded in a 8-coordinate geometry to eight Cl1- atoms. There are a spread of Eu–Cl bond distances ranging from 3.05–3.08 Å. Al3+ is bonded in a tetrahedral geometry to four Cl1- atoms. All Al–Cl bond lengths are 2.16 Å. There are four inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a distorted L-shaped geometry to one Eu2+ and one Al3+ atom. In the second Cl1- site, Cl1- is bonded in a distorted bent 120 degrees geometry to one Eu2+ and one Al3+ atom. In the third Cl1- site, Cl1- is bonded in a distorted L-shaped geometry to one Eu2+ and one Al3+ atom. In the fourth Cl1- site, Cl1- is bonded in a 1-coordinate geometry to one Eu2+ and one Al3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(Cu2Sn)2 by Materials Project

EuCu4Sn2 crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. Eu is bonded in a 8-coordinate geometry to eight equivalent Cu atoms. All Eu–Cu bond lengths are 3.77 Å. Cu is bonded in a 9-coordinate geometry to two equivalent Eu, three equivalent Cu, and four equivalent Sn atoms. There are one shorter (3.05 Å) and two longer (3.08 Å) Cu–Cu bond lengths. There are a spread of Cu–Sn bond distances ranging from 3.11–3.22 Å. Sn is bonded in a 8-coordinate geometry to eight equivalent Cu atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(InAs)2 by Materials Project

Eu(InAs)2 crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of two Eu(InAs)2 sheets oriented in the (0, 0, 1) direction. Eu2+ is bonded to six equivalent As3- atoms to form edge-sharing EuAs6 octahedra. There are four shorter (3.10 Å) and two longer (3.11 Å) Eu–As bond lengths. In2+ is bonded in a trigonal non-coplanar geometry to three equivalent As3- atoms. There are one shorter (2.75 Å) and two longer (2.76 Å) In–As bond lengths. As3- is bonded to three equivalent Eu2+ and three equivalent In2+ atoms to form a mixture of corner and edge-sharing AsEu3In3 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(C2N3)3 by Materials Project

Eu(C2N3)3 crystallizes in the orthorhombic Cmcm space group. The structure is one-dimensional and consists of four Eu(C2N3)3 ribbons oriented in the (1, 0, 0) direction. Eu3+ is bonded in a 6-coordinate geometry to six N3- atoms. All Eu–N bond lengths are 2.54 Å. There are two inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a linear geometry to two N3- atoms. There is one shorter (1.18 Å) and one longer (1.30 Å) C–N bond length. In the second C4+ site, C4+ is bonded in a linear geometry to two N3- atoms. There is one shorter (1.18 Å) and one longer (1.30 Å) C–N bond length. There are four inequivalent N3- sites. In the first N3- site, N3- is bonded in a distorted bent 120 degrees geometry to two equivalent C4+ atoms. In the second N3- site, N3- is bonded in a distorted bent 150 degrees geometry to one Eu3+ and one C4+ atom. In the third N3- site, N3- is bonded in a bent 120 degrees geometry to two equivalent C4+ atoms. In the fourth N3- site, N3- is bonded in a distorted bent 150 degrees geometry to one Eu3+ and one C4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(ReO4)2 by Materials Project

Eu(ReO4)2 crystallizes in the trigonal P-3 space group. The structure is two-dimensional and consists of one Eu(ReO4)2 sheet oriented in the (0, 0, 1) direction. Eu2+ is bonded to six equivalent O2- atoms to form EuO6 octahedra that share corners with six equivalent ReO4 tetrahedra. All Eu–O bond lengths are 2.48 Å. Re7+ is bonded to four O2- atoms to form ReO4 tetrahedra that share corners with three equivalent EuO6 octahedra. The corner-sharing octahedral tilt angles are 20°. There is one shorter (1.73 Å) and three longer (1.76 Å) Re–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Eu2+ and one Re7+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one Re7+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(MgBi)2 by Materials Project

EuMg2Bi2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Mg is bonded to four equivalent Bi atoms to form MgBi4 tetrahedra that share corners with six equivalent EuBi6 octahedra, corners with six equivalent MgBi4 tetrahedra, edges with three equivalent EuBi6 octahedra, and edges with three equivalent MgBi4 tetrahedra. The corner-sharing octahedra tilt angles range from 15–55°. There are three shorter (2.97 Å) and one longer (3.01 Å) Mg–Bi bond lengths. Eu is bonded to six equivalent Bi atoms to form EuBi6 octahedra that share corners with twelve equivalent MgBi4 tetrahedra, edges with six equivalent EuBi6 octahedra, and edges with six equivalent MgBi4 tetrahedra. All Eu–Bi bond lengths are 3.40 Å. Bi is bonded to four equivalent Mg and three equivalent Eu atoms to form a mixture of distorted edge and corner-sharing BiEu3Mg4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(NO3)3 by Materials Project

Eu(NO3)3 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of one Eu(NO3)3 sheet oriented in the (0, 0, 1) direction. Eu3+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Eu–O bond distances ranging from 2.46–2.67 Å. There are three inequivalent N5+ sites. In the first N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.25–1.28 Å. In the second N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There is two shorter (1.26 Å) and one longer (1.27 Å) N–O bond length. In the third N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There is two shorter (1.25 Å) and one longer (1.30 Å) N–O bond length. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Eu3+ and one N5+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to one Eu3+ and one N5+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Eu3+ and one N5+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to one Eu3+ and one N5+ atom. In the fifth O2- site, O2- is bonded in a distorted single-bond geometry to one Eu3+ and one N5+ atom. In the sixth O2- site, O2- is bonded in a distorted single-bond geometry to one Eu3+ and one N5+ atom. In the seventh O2- site, O2- is bonded in a distorted single-bond geometry to one Eu3+ and one N5+ atom. In the eighth O2- site, O2- is bonded in a distorted single-bond geometry to one Eu3+ and one N5+ atom. In the ninth O2- site, O2- is bonded in a distorted single-bond geometry to one Eu3+ and one N5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(GaS2)2 by Materials Project

EuGa2S4 crystallizes in the orthorhombic Fddd space group. The structure is three-dimensional. there are three inequivalent Eu2+ sites. In the first Eu2+ site, Eu2+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are a spread of Eu–S bond distances ranging from 3.09–3.14 Å. In the second Eu2+ site, Eu2+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are four shorter (3.09 Å) and four longer (3.12 Å) Eu–S bond lengths. In the third Eu2+ site, Eu2+ is bonded in a 8-coordinate geometry to eight S2- atoms. There are four shorter (3.10 Å) and four longer (3.12 Å) Eu–S bond lengths. There are two inequivalent Ga3+ sites. In the first Ga3+ site, Ga3+ is bonded to four S2- atoms to form a mixture of corner and edge-sharing GaS4 tetrahedra. There are a spread of Ga–S bond distances ranging from 2.27–2.33 Å. In the second Ga3+ site, Ga3+ is bonded to four S2- atoms to form a mixture of corner and edge-sharing GaS4 tetrahedra. There are one shorter (2.27 Å) and three longer (2.32 Å) Ga–S bond lengths. There are four inequivalent S2- sites. In the first S2- site, S2- is bonded in a 4-coordinate geometry to two Eu2+ and two Ga3+ atoms. In the second S2- site, S2- is bonded in a 4-coordinate geometry to two Eu2+ and two equivalent Ga3+ atoms. In the third S2- site, S2- is bonded in a 4-coordinate geometry to two Eu2+ and two Ga3+ atoms. In the fourth S2- site, S2- is bonded in a 4-coordinate geometry to two Eu2+ and two equivalent Ga3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(GaSe2)2 by Materials Project

EuGa2Se4 crystallizes in the orthorhombic Fddd space group. The structure is three-dimensional. there are three inequivalent Eu2+ sites. In the first Eu2+ site, Eu2+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of Eu–Se bond distances ranging from 3.23–3.28 Å. In the second Eu2+ site, Eu2+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are four shorter (3.23 Å) and four longer (3.25 Å) Eu–Se bond lengths. In the third Eu2+ site, Eu2+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are four shorter (3.22 Å) and four longer (3.27 Å) Eu–Se bond lengths. There are two inequivalent Ga3+ sites. In the first Ga3+ site, Ga3+ is bonded to four Se2- atoms to form a mixture of corner and edge-sharing GaSe4 tetrahedra. There are a spread of Ga–Se bond distances ranging from 2.41–2.46 Å. In the second Ga3+ site, Ga3+ is bonded to four Se2- atoms to form a mixture of corner and edge-sharing GaSe4 tetrahedra. There are a spread of Ga–Se bond distances ranging from 2.42–2.46 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 4-coordinate geometry to two Eu2+ and two Ga3+ atoms. In the second Se2- site, Se2- is bonded in a 4-coordinate geometry to two Eu2+ and two Ga3+ atoms. In the third Se2- site, Se2- is bonded in a 4-coordinate geometry to two Eu2+ and two equivalent Ga3+ atoms. In the fourth Se2- site, Se2- is bonded in a 4-coordinate geometry to two Eu2+ and two equivalent Ga3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Synthesis, Structural Characterization and Chemical Bonding of Sr 7 Li 6 Sn 12 and its Quaternary Derivatives with Eu and Alkaline Earth Metal (Mg, Ca, Ba) Substitutions. A Tale of Seven Li‐Containing Stannides and Two Complex Crystal Structures

In this paper, we discuss the synthesis and the structural characterization of the new ternary compound Sr 7 Li 6 Sn 12 and its six quaternary derivatives, where alkaline earth metals (Ca, Mg, Ba) and the rare earth metal Eu are substituted, yielding crystalline phases of monoclinic or orthorhombic symmetry. The title compounds were synthesized via high‐temperature solid‐state reactions of the corresponding elements. The crystal structures were determined by single‐crystal X‐ray diffraction methods. The (Sr,Ca) 7 Li 6 Sn 12 and Eu 7 (Mg,Li) 6 Sn 12 phases represent a new structure type (space group P 2/ m , No. 10) while Sr 7 Li 6 Sn 12 and the rest of the title phases crystallize in the orthorhombic base‐centered space group Cmmm (No. 65) which is similar to the Eu 7 Li 8– x Sn 10+ x ( x ≈ 2.0) phase with the Ce 7 Li 8 Ge 10 structure type (Pearson code oC 50). Careful examination of the resulting structures shows intricate disordering between Li and Sn atoms, which is governed by the total number of valence electrons. The discussion of experimental results is also supported by DFT electronic structure calculations.

Osman, Hussien H.↗
DOE OSTI2021

Structural and Spectroscopic Analysis of Ln(II) 18-crown-6 and Benzo-18-crown-6 Complexes (Ln = Sm, Eu, Yb)

Three Ln 2+ 18-crown-6 complexes of the formula Ln(18-crown-6)I 2 (Ln = Sm, Eu, Yb) were isolated from the explicit synthesis of the corresponding LnI 2 salts with 18-crown-6 and tetrabutylammonium tetraphenylborate in organic media under air-free conditions. Each metal complex forms a distorted hexagonal bipyramidal geometry and crystallizes in the monoclinic space group P2 1 /n. Comparatively, crystallization of Ln(benzo-18-crown-6)I 2 (Ln = Sm, Eu, Yb) from the reaction of LnI2 with tetrabutylammonium tetraphenylborate and benzo-18-crown-6 in THF/ethanol under similarly air-free conditions yields two polymorphs. The first form, α, crystallizes in the monoclinic space group P2 1 /c (or the nonstandard setting P2 1 /n for α-Yb); whereas the second polymorph, β, crystallizes in P$\bar{1}$. While the geometries of the molecules only vary slightly, the molecular packing and intramolecular contacts are quite different. In the structure of β, π–π interactions between the benzo- moieties of adjacent molecules are observed, whereas these interactions are absent in α. Despite the similarities in these classically 4f n+1 lanthanide systems, the complexes display distinct spectroscopic features in their respective absorption and photoluminescence spectra. Broadband 5d → 4f photoluminescence was observed for the Sm and Eu compounds in the NIR region and UV–visible region, respectively. None of the three Yb compounds exhibit photoluminescence UV–visible-NIR region; however, a unique photooxidation event was observed resulting in characteristic Yb(III) 4f → 4f transitions in the NIR region of the absorption spectra of these compounds. Finally, these findings are discussed along with structural comparisons of the 18-crown-6 and benzo-18-crown-6 compounds as well as other reported Ln(II) crown complexes in the literature.

crystals↗