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 Methyl Group Rotation and Tunnellingin Crystals of 5-Membered Ring Molecules

1988 ◽  
Vol 43 (1) ◽  
pp. 35-42 ◽  
Author(s):  
A.-S. Montjoie ◽  
W. Müller-Warmuth ◽  
Hildegard Stiller ◽  
J. Stanislawski
Keyword(s):  
Elevated Temperatures ◽  
Inelastic Neutron Scattering ◽  
Relaxation Times ◽  
Nmr Relaxation ◽  
Lattice Relaxation ◽  
Inelastic Neutron ◽  
Spin Lattice Relaxation ◽  
Relaxation Rates ◽  
Quantum Tunnelling ◽  
Spin Lattice

Abstract1H NMR spin-lattice relaxation times T1 and -if accessible -level-crossing peaks and inelastic neutron scattering spectra have been measured for solid 2-and 3-methylfuran, 2-and 3-methylthiophene, 3-and 4-methylpyrazole, 1-methylimidazole, and 5-methylisoxazole. From the tunnel splittings, the torsional excitations and the NMR relaxation rates, the molecular dynamics of the methyl rotators has been evaluated between the limits of quantum tunnelling at low temperatures and thermally activated random reorientation at elevated temperatures.

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 Putting the Squeeze on Molecule-Based Magnets: Exploiting Pressure to Develop Magneto-Structural Correlations in Paramagnetic Coordination Compounds

2020 ◽  
Author(s):  
Euan Brechin ◽  
Alvaro Etcheverry-Berrios ◽  
Simon Parsons ◽  
Konstantin Kamenev ◽  
Michael Probert ◽  
...  
Keyword(s):  
High Pressure ◽  
Structural Changes ◽  
Inelastic Neutron Scattering ◽  
Magnetic Ordering ◽  
Exchange Interactions ◽  
Inelastic Neutron ◽  
Magnetic Core ◽  
Magnetic Behaviour ◽  
Paramagnetic Resonance ◽  
Bond Angles

The cornerstone of molecular magnetism is a detailed understanding of the relationship between structure and magnetic behaviour, i.e. the development of magneto-structural correlations. Traditionally, the synthetic chemist approaches this challenge by making multiple compounds that share a similar magnetic core but differ in peripheral ligation. Changes in the ligand framework induce changes in the bond angles and distances around the metal ions which are manifested in changes to magnetic susceptibility and magnetisation data. This approach requires the synthesis of series of different ligands and assumes that the chemical/electronic nature of the ligands and their coordination to the metal, the nature and number of counter ions and how they are positioned in the crystal lattice, and the molecular and crystallographic symmetry have no effect on the measured magnetic properties. In short, the assumption is that everything outwith the magnetic core is innocent, which is a huge oversimplification. The ideal scenario would be to have the same complex available in multiple structural conformations, and this is something that can be achieved through the application of external hydrostatic pressure, correlating structural changes observed through high pressure single crystal X-ray crystallography with changes observed in high pressure magnetometry, in tandem with high pressure inelastic neutron scattering (INS), high pressure electron paramagnetic resonance (EPR) spectroscopy and high pressure absorption/emission/Raman spectroscopy. In this review, which summarises our work in this area over the last 15 years, we show that the application of pressure to molecule-based magnets can (reversibly): (1) lead to changes in bond angles, distances and Jahn-Teller orientations; (2) break and form bonds; (3) induce polymerisation/depolymerisation; (4) enforce multiple phase transitions; (5) instigate piezochromism; (6) change the magnitude and sign of pairwise exchange interactions and magnetic anisotropy and (7) lead to significant increases in magnetic ordering temperatures.

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