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.

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.

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 Isotropic Nature of the Metallic Kagome Ferromagnet Fe3Sn2 at High Temperatures

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 307
Author(s):  
Rebecca L. Dally ◽  
Daniel Phelan ◽  
Nicholas Bishop ◽  
Nirmal J. Ghimire ◽  
Jeffrey W. Lynn
Keyword(s):  
Elevated Temperatures ◽  
Magnetocrystalline Anisotropy ◽  
Inelastic Neutron Scattering ◽  
Exchange Interactions ◽  
Inelastic Neutron ◽  
Temperature Threshold ◽  
Magnetic Exchange ◽  
Spatial Anisotropy ◽  
Isotropic Exchange ◽  
State Spin

Anisotropy and competing exchange interactions have emerged as two central ingredients needed for centrosymmetric materials to exhibit topological spin textures. Fe3Sn2 is thought to have these ingredients as well, as it has recently been discovered to host room temperature skyrmionic bubbles with an accompanying topological Hall effect. We present small-angle inelastic neutron scattering measurements that unambiguously show that Fe3Sn2 is an isotropic ferromagnet below TC≈660 K to at least 480 K—the lower temperature threshold of our experimental configuration. Fe3Sn2 is known to have competing magnetic exchange interactions, correlated electron behavior, weak magnetocrystalline anisotropy, and lattice (spatial) anisotropy; all of these features are thought to play a role in stabilizing skyrmions in centrosymmetric systems. Our results reveal that at the elevated temperatures measured, there is an absence of significant magnetocrystalline anisotropy and that the system behaves as a nearly ideal isotropic exchange interaction ferromagnet, with a spin stiffness D(T=480 K)=168 meV Å2, which extrapolates to a ground state spin stiffness D(T=0 K)=231 meV Å2.

scholarly journals Signatures of a liquid-crystal transition in spin-wave excitations of skyrmions

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Narayan Mohanta ◽  
Andrew D. Christianson ◽  
Satoshi Okamoto ◽  
Elbio Dagotto
Keyword(s):  
Spin Wave ◽  
Magnetic Order ◽  
Inelastic Neutron Scattering ◽  
Spin Dynamics ◽  
Wave Spectrum ◽  
Exchange Interactions ◽  
Inelastic Neutron ◽  
Spin Wave Excitations ◽  
Crystal Transition ◽  
Dynamics Simulations

AbstractUnderstanding the spin-wave excitations of chiral magnetic order, such as the skyrmion crystal (SkX), is of fundamental interest to confirm such exotic magnetic order. The SkX is realized by competing Dzyaloshinskii-Moriya and ferromagnetic-exchange interactions with a magnetic field or anisotropy. Here, we compute the dynamical spin structure factor, using Monte Carlo and spin dynamics simulations, extracting the spin-wave spectrum in the SkX, in the vicinity of the paramagnet to SkX transition. Inside the SkX, we find six spin-wave modes, which are supplemented by another mode originating from the ferromagnetic background. Above the critical temperature Ts for the skyrmion crystallization, we find a diffusive regime, reminiscent of the liquid-to-crystal transition, revealing that topological spin texture of skyrmionic character starts to develop above Ts as the precursor of the SkX. We discuss the opportunities for the detection of the spin waves of the SkX using inelastic-neutron-scattering experiments in manganite-iridate heterostructures.

EXACT SOLUTIONS IN A SPATIALLY ANISOTROPIC QUANTUM SPIN LADDER MODEL HAVING TWO- AND FOUR-SPIN EXCHANGE INTERACTIONS

2009 ◽  
Vol 23 (08) ◽  
pp. 1981-2019 ◽  
Author(s):  
J. H. BARRY ◽  
J. D. COHEN ◽  
M. W. MEISEL
Keyword(s):  
Spin Exchange ◽  
Inelastic Neutron Scattering ◽  
Exchange Interactions ◽  
Inelastic Neutron ◽  
Elementary Excitation ◽  
Quantum Spin ◽  
Quantum Model ◽  
Spin Ladder ◽  
Zero Field ◽  
Ladder Model

We consider a two-leg S=1/2 quantum spin ladder model with two-spin (intra-rung) and four-spin (inter-rung) Heisenberg exchange interactions and a uniform magnetic field. Exact mappings are derived connecting the partition function and correlations in the three-parameter quantum model to those known in a two-parameter Ising chain. The quantum phase diagram of the ladder magnet is determined. Static correlations provide pertinent correlation lengths and underlie spatial fluctuation behaviors at arbitrary temperatures, including quantum fluctuations at absolute zero. Dynamic correlations in zero field are used to obtain an exact solution for the inelastic neutron scattering function Sxx(q, ω) at all temperatures, explicitly yielding the elementary excitation spectrum.

Abstract: Exchange interactions in Cs3Cr2Cl9: Inelastic neutron scattering studies

1982 ◽  
Vol 53 (3) ◽  
pp. 1996-1996 ◽  
Author(s):  
A. Stebler ◽  
H. U. Güdel ◽  
A. Furrer ◽  
J. Kjems
Keyword(s):  
Neutron Scattering ◽  
Inelastic Neutron Scattering ◽  
Exchange Interactions ◽  
Inelastic Neutron ◽  
Abstract Exchange

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.

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