scholarly journals Dirac Magnons and Topological Energy Gaps in Honeycomb Magnets

2020 ◽  
Vol 29 (6) ◽  
pp. 8-13
Author(s):  
Jae-Ho CHUNG
Keyword(s):  
Electronic Materials ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Linear Dispersion ◽  
Dirac Particles ◽  
Energy Gaps ◽  
Theoretical Predictions ◽  
Momentum Spectra ◽  
Van Der Waals Materials ◽  
Magnon Excitation

Fermionic Dirac particles have long been known to exist in electronic materials exhibiting linear dispersion relations within energy-momentum spectra, such as two-dimensional graphene. Recently, a bosonic version of Dirac particles was predicted to appear in the magnon excitation structures of honeycomb magnets. In this article, we review theoretical predictions of topological Dirac magnons in honeycomb ferromagnets, and their experimental observations using inelastic neutron scattering in Cr-based van der Waals materials.

QUANTIZED INTRINSICALLY LOCALIZED MODES: LOCALIZATION THROUGH INTERACTION

2012 ◽  
Vol 11 ◽  
pp. 12-21
Author(s):  
PETER S. RISEBOROUGH
Keyword(s):  
Neutron Scattering ◽  
Experimental Observation ◽  
Phonon Spectrum ◽  
Bound States ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Localized Modes ◽  
Scattering Spectrum ◽  
Theoretical Predictions ◽  
Quartic Anharmonicity

We have calculated the lowest energy quantized spectra of Intrinsically Localized Modes (ILMs) for the Fermi-Pasta-Ulam lattices. The quantized ILM spectra are composed of resonances in the two-phonon continuum and branches of infinitely long-lived excitations that are bound states formed from even numbers of phonons. For quartic anharmonicity and one atom per unit cell, the calculated ILMs are consistent with the results of previous calculations using the number conserving approximation. However, by contrast the ILM spectrum of the lattice with cubic interactions couples resonantly with the single-phonon spectrum and cannot be calculated within a number conserving approximation. Furthermore we argue that, by introducing a sufficiently strong cubic non-linearity, the quantized ILMs can be observed directly through the single-phonon inelastic neutron scattering spectrum. We compare our theoretical predictions with the recent experimental observation of breathers in NaI by Manley et al.

scholarly journals Suppressed-moment 2-k order in the canonical frustrated antiferromagnet Gd2Ti2O7

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Joseph A. M. Paddison ◽  
Georg Ehlers ◽  
Andrew B. Cairns ◽  
Jason S. Gardner ◽  
Oleg A. Petrenko ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Spin Wave ◽  
Inelastic Neutron Scattering ◽  
Magnetic Moments ◽  
Magnetic Ordering ◽  
Thermal Fluctuation ◽  
Inelastic Neutron ◽  
Scattering Measurements ◽  
Theoretical Predictions ◽  
Powder Samples

AbstractIn partially ordered magnets, order and disorder coexist in the same magnetic phase, distinct from both spin liquids and spin solids. Here, we determine the nature of partial magnetic ordering in the canonical frustrated antiferromagnet Gd2Ti2O7, in which Gd3+ spins occupy a pyrochlore lattice. Using single-crystal neutron-diffraction measurements in applied magnetic field, magnetic symmetry analysis, inelastic neutron-scattering measurements, and spin-wave modeling, we show that its low-temperature magnetic structure involves two propagation vectors (2-k structure) with suppressed ordered magnetic moments and enhanced spin-wave fluctuations. Our experimental results are consistent with theoretical predictions of thermal fluctuation-driven order in Gd2Ti2O7, and reveal that inelastic neutron-scattering measurements on powder samples can solve the longstanding problem of distinguishing single-k and multi-k magnetic structures.

Magnetic Specific Heat of Cd1−xMnxTe at Low Temperatures and High Magnetic Fields

1986 ◽  
Vol 89 ◽  
Author(s):  
W. Y. Ching ◽  
D. L. Huber
Keyword(s):  
Specific Heat ◽  
Low Temperatures ◽  
Inelastic Neutron Scattering ◽  
Exchange Interactions ◽  
Dynamic Structure ◽  
Inelastic Neutron ◽  
Magnetic Specific Heat ◽  
Theoretical Predictions ◽  
Use Values ◽  
Applied Fields

AbstractTheoretical predictions for the magnetic specific heat of Cd1−xMnxTe:x=0.20, 0.35, 0.50, and 0.65 are reported for B=0, 10T, and 100T. The analysis applies to the low-temperature regime, T≤10K, where the fundamental excitations are harmonic magnons. The calculations use values for the exchange interactions which were inferred from fits to the dynamic structure factor describing inelastic neutron scattering at low temperatures. For x=0.35, 0.50, and 0.65 the specific heat is only weakly affected by applied fields up to 10T. At the lowest concentration the application of a field of 10T leads to a significant reduction in the specific heat. Results are also presented for the distribution of magnon modes at various concentrations and fields.

Single-particle dynamics of the solid heliums from deep inelastic neutron scattering

1987 ◽  
Vol 65 (11) ◽  
pp. 1401-1408 ◽  
Author(s):  
R. O. Simmons
Keyword(s):  
Neutron Scattering ◽  
Single Particle ◽  
Inelastic Neutron Scattering ◽  
Solid Helium ◽  
Dynamic Structure ◽  
Inelastic Neutron ◽  
Hexagonal Close Packed ◽  
Theoretical Predictions ◽  
Atomic Momentum ◽  
Particle Property

Previous neutron-scattering research on solid heliums has been restricted to small momentum transfers, Q, both by large Debye–Waller factors and by scientific interest being restricted to collective modes and their interactions. It has also been limited by insufficient sources of neutron beams of about an electronvolt in energy, which are required to apply the method of deep inelastic scattering to solids. Making use of a spallation neutron source and a suitable chopper spectrometer, one can now collect data in which the dynamic structure factor S(Q,E) directly reflects the atomic-momentum distribution n(p). For 4He, the major determining factor on this single-particle property is the density of the sample, not its microscopic structure. At a strictly constant number density, samples of hexagonal close-packed (hcp), body-centered cubic (bcc), and normal liquid show identical S(Q,E)'s for Q's near 200 nm−1, at current levels of precision. The case of bcc 4He is used to illustrate the method, and the derived kinetic energy is compared with theoretical predictions. The applicability of these results in other areas of solid-helium physics is indicated.

scholarly journals Широкополосная ЭПР-спектроскопия кристалла SrY-=SUB=-2-=/SUB=-O-=SUB=-4-=/SUB=-:Ho-=SUP=-3+-=/SUP=-

2022 ◽  
Vol 130 (1) ◽  
pp. 28
Author(s):  
Г.С. Шакуров ◽  
Б.З. Малкин ◽  
Р.Г. Батулин ◽  
А.Г. Киямов
Keyword(s):  
Hyperfine Structure ◽  
Single Crystals ◽  
Crystal Field ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Zero Field ◽  
Frequency Range ◽  
Energy Gaps ◽  
Scattering Spectra ◽  
Structure Constants

EPR spectra of impurity Ho3+ ions in oriented SrY2O4 single-crystals are registered at the temperature 4.2 K in the frequency range from 70 to 180 GHz. The results of measurements evidence for the substitution of Ho3+ ions for the Y3+ ions at the structurally nonequivalent sites R1 and R2 with the local Cs point symmetry. The values of g-factors, hyperfine structure constants and the energy gaps berween the ground and the first excited non-degenherate crystal-field sublevels of the ground 5I8 multiplet are determined. The observed specific features of the ground states of Но3+ ions (non-Kramers doublets with the zero-field splittings of 4.30 and 1.67 cm-1) open a possibility to identify transitions in optical spectra of SrY2O4:Ho and inelastic neutron scattering spectra of SrHo2O4 crystals.

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 study of icosahedral AlFeCu quasicrystal

1992 ◽  
Vol 2 (2) ◽  
pp. 125-130 ◽  
Author(s):  
M. Quilichini ◽  
B. Hennion ◽  
G. Heger ◽  
S. Lefebvre ◽  
A. Quivy
Keyword(s):  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Scattering Study ◽  
Neutron Scattering Study
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