scholarly journals Filled Skutterudite Antimonides: Validation of the Electron-Crystal Phonon-Glass Approach to New Thermoelectric Materials

1997 ◽  
Vol 478 ◽  
Author(s):  
D. Mandrus ◽  
B. C. Sales ◽  
V. Keppens ◽  
B. C. Chakoumakos ◽  
P. Dai ◽  
...  
Keyword(s):  
Specific Heat ◽  
Thermoelectric Materials ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Low Energy ◽  
Vibrational Modes ◽  
Weakly Bound ◽  
Filled Skutterudite ◽  
Resonant Ultrasound ◽  
Electron Crystal

AbstractAfter a brief review of the transport and thermoelectric properties of filled skutterudite antimonides, we present resonant ultrasound, specific heat, and inelastic neutron scattering results that establish the existence of two low-energy vibrational modes in the filled skutterudite LaFe3CoSb12. It is likely that at least one of these modes represents the localized, incoherent vibrations of the La ion in an oversized atomic “cage.” These results support the usefulness of weakly bound, “rattling” ions for the improvement of thermoelectric performance.

The Dynamics of the Guests in Filled Germanium Clathrates

2005 ◽  
Vol 886 ◽  
Author(s):  
Raphael P. Hermann ◽  
Fernande Grandjean ◽  
Veerle Keppens ◽  
Werner Schweika ◽  
George S. Nolas ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Nuclear Inelastic Scattering ◽  
Vibrational Modes ◽  
Weakly Bound ◽  
Typical Time ◽  
Tunneling Dynamics ◽  
Time And Energy ◽  
Localized Vibrational Modes

ABSTRACTIn the filled gallium-germanium clathrates, R8Ga16Ge30, where R is Ba, Sr, or Eu, the guests are located in two large cages and are weakly bound to the crystalline clathrate framework. The caged guests exhibit a localized “rattling” vibrational mode that provides an efficient mechanism for reducing the thermal conductivity. Inelastic neutron scattering and nuclear inelastic scattering measurements have yielded the phonon density of states in R8Ga16Ge30; the line width of the localized vibrational modes is found to be an important parameter in determining the lattice thermal conductivity. Neutron diffraction studies on R8Ga16Ge30 have shown that the guests in the larger cage are located off-center, and it was proposed that their jumping about the four off-center locations is responsible for the observed glass-like thermal conductivity at temperatures below 10 K. The detection of such slow guest motion is challenging because the typical time and energy scales involved are ca. 4 ns and 1 µeV, respectively. We have studied the slow europium tunneling dynamics in Eu4Sr4Ga16Ge30 by both Mössbauer and microwave absorption spectroscopy.

scholarly journals An inelastic neutron scattering study of dietary phenolic acids

2014 ◽  
Vol 16 (16) ◽  
pp. 7491-7500 ◽  
Author(s):  
M. Paula M. Marques ◽  
Luís A. E. Batista de Carvalho ◽  
Rosendo Valero ◽  
Nelson F. L. Machado ◽  
Stewart F. Parker
Keyword(s):  
Dft Calculations ◽  
Antioxidant Capacity ◽  
Spectral Region ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Low Energy ◽  
Vibrational Modes ◽  
Conformational Preferences ◽  
Scattering Study ◽  
Neutron Scattering Study

The conformational preferences of dietary phenols were determined by INS spectroscopy and DFT calculations. Access to the low energy spectral region enabled the identification of vibrational modes associated with H-type interactions, which are the determinants of the antioxidant capacity.

scholarly journals Dynamical and thermal magnetic properties of the Kitaev spin liquid candidate α-RuCl3

2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Pontus Laurell ◽  
Satoshi Okamoto
Keyword(s):  
Magnetic Properties ◽  
Specific Heat ◽  
Inelastic Neutron Scattering ◽  
Current Model ◽  
Inelastic Neutron ◽  
Low Energy ◽  
Spin Liquid ◽  
Hamiltonian Description ◽  
Interaction Terms ◽  
Magnetic Specific Heat

AbstractWhat is the correct low-energy spin Hamiltonian description of $$\alpha$$α-RuCl$$_{3}$$3? The material is a promising Kitaev spin liquid candidate, but is also known to order magnetically, the description of which necessitates additional interaction terms. The nature of these interactions, their magnitudes and even signs, remain an open question. In this work we systematically investigate dynamical and thermodynamic magnetic properties of proposed effective Hamiltonians. We calculate zero-temperature inelastic neutron scattering (INS) intensities using exact diagonalization, and magnetic specific heat using a thermal pure quantum states method. We find that no single current model satisfactorily explains all observed phenomena of $$\alpha$$α-RuCl$$_{3}$$3. In particular, we find that Hamiltonians derived from first principles can capture the experimentally observed high-temperature peak in the magnetic specific heat, while overestimating the magnon energy at the zone center. In contrast, other models reproduce important features of the INS data, but do not adequately describe the magnetic specific heat. To address this discrepancy we propose a modified ab initio model that is consistent with both magnetic specific heat and low-energy features of INS data.

Anomalous vibrational modes in acetanilide as studied by inelastic neutron scattering

1992 ◽  
Vol 2 (10) ◽  
pp. 1929-1939 ◽  
Author(s):  
Mariette Barthes ◽  
Juegen Eckert ◽  
Susanna W. Johnson ◽  
Jacques Moret ◽  
Basil I. Swanson ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Vibrational Modes

Inelastic neutron scattering and low-energy excitation of amorphous SF6 hydrate prepared by vapor-deposition technique

2003 ◽  
Vol 81 (1-2) ◽  
pp. 107-114 ◽  
Author(s):  
O Yamamuro ◽  
T Matsuo ◽  
I Tsukushi ◽  
N Onoda-Yamamuro
Keyword(s):  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Annealed Sample ◽  
Low Energy ◽  
Energy Excitation ◽  
Hydrogen Bond Formation ◽  
Crystalline Sample ◽  
Two Samples ◽  
Vapor Deposition Technique

Amorphous SF6 hydrate (SF6·17H2O) was prepared by depositing the mixed vapor onto a substrate kept at about 8 K. The inelastic neutron-scattering spectra of the as-deposited sample and those annealed at about 120 and 150 K were measured at 50 K in the energy range below 100 meV. The first two samples were considered to be in amorphous states while the third one was in a crystalline state. The librational frequency of the water molecule (at around 60 meV) is smaller in the order of (as-deposited sample) < (annealed sample) < (crystalline sample). This indicates that the strength of the intermolecular hydrogen bonds is (crystalline sample) > (annealed sample) > (as-deposited sample). The spectra below 10 meV were compared with our previous data of pure vapor-deposited amorphous ices and those doped with methanol (CD3OH). The low-energy excitation (E < 6 meV) differed drastically depending on the dopants, i.e., the scattering intensity was enhanced by methanol doping but reduced by SF6 doping. This may be because the hydrogen-bond formation was hindered by methanol doping but promoted rather more by SF6 doping because of the hydrophobic interaction as in clathrate hydrates. PACS Nos.: 61.12Ex, 63.50tx

Spin Dynamics in the Metallic State of YBa2(Cu0.98 Zn0.02) 3O6+x

1998 ◽  
Vol 12 (29n31) ◽  
pp. 3330-3334 ◽  
Author(s):  
Y. Sidis ◽  
P. Bourges ◽  
B. Hennion ◽  
R. Villeneuve ◽  
G. Collin ◽  
...  
Keyword(s):  
Inelastic Neutron Scattering ◽  
Spin Dynamics ◽  
Inelastic Neutron ◽  
Resonance Peak ◽  
Low Energy ◽  
Metallic State ◽  
Magnetic Fluctuations ◽  
Local Enhancement ◽  
Compound I ◽  
Nonmagnetic Impurities

Inelastic neutron scattering measurements have been carried out on a YBa2(Cu0.98-Zn0.02)3O 6+x single crystal in both underdoped (x = 0.7) and overdoped (x = 0.97) regimes. In the zinc substituted system, spin dynamics is drastically changed in respect to the pure compound: (i) the "resonance peak" almost vanishes, (ii) the spin gap is filled, (iii) new antiferromagnetic excitations are found at low energy. These new magnetic fluctuations, which persist in the normal state, account for a local enhancement of AF correlations around nonmagnetic impurities. Besides, it is worth emphasizing that features, not directly related to superconductivity, i.e., the contribution to the spin dynamics apart from the resonance peak and the "spin pseudo-gap" observed in the underdoped regime above T c , coexist with the new low energy magnetic fluctuations.

scholarly journals Decay and renormalization of a longitudinal mode in a quasi-two-dimensional antiferromagnet

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Seung-Hwan Do ◽  
Hao Zhang ◽  
Travis J. Williams ◽  
Tao Hong ◽  
V. Ovidiu Garlea ◽  
...  
Keyword(s):  
Inelastic Neutron Scattering ◽  
Longitudinal Mode ◽  
Wave Theory ◽  
Inelastic Neutron ◽  
Low Energy ◽  
Many Body ◽  
Longitudinal Modes ◽  
Quantum Magnet ◽  
Energy Mode ◽  
The Many

AbstractAn ongoing challenge in the study of quantum materials, is to reveal and explain collective quantum effects in spin systems where interactions between different modes types are important. Here we approach this problem through a combined experimental and theoretical study of interacting transverse and longitudinal modes in an easy-plane quantum magnet near a continuous quantum phase transition. Our inelastic neutron scattering measurements of Ba2FeSi2O7 reveal the emergence, decay, and renormalization of a longitudinal mode throughout the Brillouin zone. The decay of the longitudinal mode is particularly pronounced at the zone center. To account for the many-body effects of the interacting low-energy modes in anisotropic magnets, we generalize the standard spin-wave theory. The measured mode decay and renormalization is reproduced by including all one-loop corrections. The theoretical framework developed here is broadly applicable to quantum magnets with more than one type of low energy mode.

Inelastic neutron scattering study of low-energy excitations in vapor-deposited glassy propylene

1997 ◽  
Vol 106 (8) ◽  
pp. 2997-3002 ◽  
Author(s):  
Osamu Yamamuro ◽  
Itaru Tsukushi ◽  
Takasuke Matsuo ◽  
Kiyoshi Takeda ◽  
Toshiji Kanaya ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Low Energy ◽  
Scattering Study ◽  
Neutron Scattering Study
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