Raman and NMR spectroscopic and theoretical investigations of the cubic laves-phases REAl<sub>2</sub> (RE = Sc, Y, La, Yb, Lu)

Gießelmann, Elias C. J.; Engel, Stefan; Kostusiak, Weronika; Zhang, Yuemei; Herbeck-Engel, Petra; Kickelbick, Guido; Janka, Oliver

doi:10.1039/d3dt00141e

Cited by 7 publications

(10 citation statements)

References 60 publications

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“…In a recent 27 Al-NMR and Raman spectroscopic study, the partially divalent character of Yb in the cubic Laves phase YbAl 2 at room temperature was investigated by comparing the s electron densities with the observed isotropic resonance shifts δ( 27 Al). Here, Yb is not comparable to the results obtained for the formally trivalent diamagnetic members of the series …”

Section: Magnetic Resonance Spectroscopycontrasting

confidence: 94%

“…Here, Yb is not comparable to the results obtained for the formally trivalent diamagnetic members of the series. 294 The Kondo semiconductor YbB 12 (UB 12 type, space group Fm3m) has been characterized at low temperatures using 11 B as well as 171 Yb NMR spectroscopy. 295,296 It was possible to observe a spin−echo signal at temperatures below 15 K for 171 Yb.…”

Section: Yb Nmrmentioning

confidence: 99%

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On the Ytterbium Valence and the Physical Properties in Selected Intermetallic Phases

Engel,

Gießelmann,

Reimann

et al. 2024

ACS Org. Inorg. Au

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The present review summarizes important aspects of the crystal chemistry of ytterbium-based intermetallic compounds along with a selection of their outstanding physical properties. These originate in many cases from the ytterbium valence. Different valence states are possible here, divalent (4f 14 ), intermediate-valent, or trivalent (4f 13 ) ytterbium, resulting in simple diamagnetic, Pauli or Curie−Weiss paramagnetic, or valence fluctuating behavior. Especially, some of the Yb 3+ intermetallics have gained deep interest due to their Kondo or heavy Fermion ground states. We have summarized their property investigations using magnetic and transport measurements, specific heat data, NMR, ESR, and Mossbauer spectroscopy, elastic and inelastic neutron scattering, and XAS data as well as detailed thermoelectric measurements.

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Section: Magnetic Resonance Spectroscopycontrasting

confidence: 94%

Section: Yb Nmrmentioning

confidence: 99%

On the Ytterbium Valence and the Physical Properties in Selected Intermetallic Phases

Engel,

Gießelmann,

Reimann

et al. 2024

ACS Org. Inorg. Au

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“…The main resonance is observed at δ = −673 ppm, which is significantly different compared to the majority of investigated intermetallic aluminum compounds. For example, the binary alkaline-earth and rare-earth dialuminides exhibit positive resonance shifts of δ = +1091 and +1152 ppm for AE Al 2 ( AE = Ca and Sr) and δ = +213 to +924 ppm for RE Al 2 ( RE = Sc, Y, La, Yb, Lu) . Ternary aluminum intermetallics also exhibit positive shifts, e.g., δ = 440–851 (Sc T 2 Al and Sc( T , T ′) 2 Al; T = T ’ = Ni, Pd, Pt, Cu, Ag, Au), 762 and 1031 (Ba 3 Pt 4 Al 4 ), 273–636 ppm ( RET 5 Al 2 ; RE = Y, Lu; T = Pd, Pt), or 419–767 ( MT Al 2 ; M = Ca-Ba, Sc, Y, La, Lu; T = Ni, Pd, Pt). , Negative 27 Al NMR shifts, in contrast, are scarce and have, to the best of our knowledge, only been observed for the binary compounds VAl 3 (δ = −170 and −100/–97 and −130 ppm), Fe 4 Al 13 (δ = −175 ppm) and TiAl (δ = −170 ppm).…”

Section: Resultsmentioning

confidence: 99%

“…For example, the binary alkaline-earth and rare-earth dialuminides exhibit positive resonance shifts of δ = +1091 and +1152 ppm for AEAl 2 (AE = Ca and Sr) 110 and δ = +213 to +924 ppm for REAl 2 (RE = Sc, Y, La, Yb, Lu). 111 Ternary aluminum intermetallics also exhibit positive shifts, e.g., δ = 440−851 (ScT 2 Al and Sc(T,T′) 2 Al; T = T' = Ni, Pd, Pt, Cu, Ag, Au), 103 762 and 1031 (Ba 3 Pt 4 Al 4 ), 105 273−636 ppm Two competing magnetic screening mechanisms were described by Ferreira: the so-called Knight shift that originates from the hyperfine interaction between the nucleus with the spins of itinerant (conduction) electrons and the hyperfine interaction with local magnetic moments at the transition metal site. While the Knight contribution leads to a deshielding at the Al atoms (and therefore a strong positive shift), the latter contribution can counter compensate this effect.…”

Section: Solid Solution and Crystal Chemistrymentioning

confidence: 99%

Formation of the Sub-oxide Sc₄Au₂O_1–x and the Drastically Negative ²⁷Al NMR Shift in Sc₂Al

et al. 2023

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During attempts to synthesize Sc4AuAl in the cubic Gd4RhIn-type structure, the solid solution Sc2Au0.5Al0.5 in the PbCl2-type structure formed instead. Subsequently, the solid solution Sc2Au1–x Al x was investigated with respect to its existence range along with the structure types formed for different compositions with x = 0, 0.25, 0.5, 0.75, and 1. According to X-ray powder diffraction studies, Sc2Al and nominal Sc2Au0.25Al0.75 crystallized in the hexagonal Ni2In-type structure (P63/mmc), while Sc2Au0.5Al0.5, Sc2Au0.75Al0.25, and Sc2Au were found to crystallize in the orthorhombic PbCl2-type structure (Pnma). The crystal structures of Sc2Au and Sc2Au0.59(1)Al0.41(1) were refined from single-crystal data (Sc2Au: a = 648.0(1), b = 467.2(1), c = 835.2(2) pm, wR2 = 0.0382, 535 F 2 values, 25 variables; Sc2Au0.59(1)Al0.41(1): a = 632.48(5), b = 472.16(3), c = 848.67(6) pm, wR2 = 0.0484, 540 F 2 values, 21 variables). Contamination with air during the synthesis of Sc2Au led to the discovery of a compound adopting the cubic W4Co2C-type structure (stuffed cubic Ti2Ni type). Using Sc2O3 as a defined oxygen source led to samples with high amounts of Sc4Au2O1–x . All intermetallic compounds exhibited Pauli paramagnetic behavior in the investigated temperature range of 2.1 to 300 K, and no superconductivity was observed at low temperatures and low fields. Sc2Au and Sc2Al were investigated by 27Al and 45Sc solid-state NMR investigations. For Sc2Al, one signal was found in the 27Al NMR spectra in line with the crystal structure; however, an extremely negative resonance shift of δ = −673 ppm was observed. In both compounds, two Sc resonances were observed, in line with the proposed crystal structure. Finally, it was observed that the stability of Sc2Au in air is limited. This was investigated via thermal analysis and (temperature-dependent) powder X-ray diffraction. DFT calculations helped in assessing charge analysis, electronic properties, and chemical bonding.

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“…2006, 221, issues 5−7) including eulogies on Laves work 1,2,10 and summarizing different aspects of the work on Laves phases. 11−15 Recently, we reported on the 27 Al NMR spectroscopic properties of the cubic MAl 2 phases 16,17 as well as on a new series of rare-earth-based Laves phases with the composition RE 2 TiAl 3 (RE = Y, Gd−Tm, Lu). 18 The striking feature of the latter is that these compounds are the first aluminum-based representatives that adopt the rhombohedral Mg 2 Ni 3 Si type structure (R3̅ m), which can be derived from the cubic Laves phase.…”

Section: ■ Introductionmentioning

confidence: 99%

Searching for Laves Phase Superstructures: Structural and ²⁷Al NMR Spectroscopic Investigations in the Hf–V–Al System

Gießelmann,

Engel,

Baldauf

et al. 2024

Inorg. Chem.

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Laves phases exhibit a plethora of different structures and a multitude of physical properties. Investigations in the ternary system Hf−V−Al led to the discovery of numerous members of the solid solution Hf(V 1−x Al x ) 2 , which adopt the hexagonal MgZn 2 type (C14) for medium to high amounts of Al (x = 0.2−1) and the cubic MgCu 2 type (C15) for small Al amounts (x = 0.05−0.1). While all members exhibit Pauli-paramagnetic behavior due to the absence of localized magnetic moments, the V-rich cubic member Hf(V 0.95 Al 0.05 ) 2 additionally exhibits a superconducting state below T C = 7.6(1) K. All synthesized compounds were characterized by powder X-ray diffraction, and selected samples were furthermore investigated by 27 Al solid-state magic-angle spinning (MAS) NMR. HfAl 2 exhibits two Al resonances, one rather sharp and one significantly broadened signal, in line with the crystal structure and respective coordination environments. The members of the solid solution exhibit extremely broadened resonances due to the mixing of V and Al on the same crystallographic sites. For nominal Hf(V 0.125 Al 0.875 ) 2 , however, two distinct sharp NMR signals were observed. This contrasts with the description of a solid solution. Therefore, single-crystal X-ray studies were conducted, showing that Hf(V 0.125 Al 0.875 ) 2 really is an ordered compound with the sum formula Hf 4 VAl 7 (P3̅ m1), which exhibits an, thus far, unknown superstructure of MgZn 2 .

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Raman and NMR spectroscopic and theoretical investigations of the cubic laves-phases REAl₂ (RE = Sc, Y, La, Yb, Lu)

Abstract: The cubic Laves-phase aluminides REAl2 with RE = Sc, Y, La, Yb and Lu were prepared from the elements by arc-melting or using refractory metal ampoules and induction heating. They...

Cited by 7 publications

References 60 publications

On the Ytterbium Valence and the Physical Properties in Selected Intermetallic Phases

On the Ytterbium Valence and the Physical Properties in Selected Intermetallic Phases

Formation of the Sub-oxide Sc₄Au₂O_1–x and the Drastically Negative ²⁷Al NMR Shift in Sc₂Al

Searching for Laves Phase Superstructures: Structural and ²⁷Al NMR Spectroscopic Investigations in the Hf–V–Al System

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Raman and NMR spectroscopic and theoretical investigations of the cubic laves-phases REAl2 (RE = Sc, Y, La, Yb, Lu)

Abstract: The cubic Laves-phase aluminides REAl2 with RE = Sc, Y, La, Yb and Lu were prepared from the elements by arc-melting or using refractory metal ampoules and induction heating. They...

Cited by 7 publications

References 60 publications

On the Ytterbium Valence and the Physical Properties in Selected Intermetallic Phases

On the Ytterbium Valence and the Physical Properties in Selected Intermetallic Phases

Formation of the Sub-oxide Sc4Au2O1–x and the Drastically Negative 27Al NMR Shift in Sc2Al

Searching for Laves Phase Superstructures: Structural and 27Al NMR Spectroscopic Investigations in the Hf–V–Al System

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Raman and NMR spectroscopic and theoretical investigations of the cubic laves-phases REAl₂ (RE = Sc, Y, La, Yb, Lu)

Formation of the Sub-oxide Sc₄Au₂O_1–x and the Drastically Negative ²⁷Al NMR Shift in Sc₂Al

Searching for Laves Phase Superstructures: Structural and ²⁷Al NMR Spectroscopic Investigations in the Hf–V–Al System