Search results for "Spin wave"
showing 10 items of 50 documents
Multiscale model approach for magnetization dynamics simulations
2016
Simulations of magnetization dynamics in a multiscale environment enable the rapid evaluation of the Landau-Lifshitz-Gilbert equation in a mesoscopic sample with nanoscopic accuracy in areas where such accuracy is required. We have developed a multiscale magnetization dynamics simulation approach that can be applied to large systems with spin structures that vary locally on small length scales. To implement this, the conventional micromagnetic simulation framework has been expanded to include a multiscale solving routine. The software selectively simulates different regions of a ferromagnetic sample according to the spin structures located within in order to employ a suitable discretization…
Exchange stiffness in the Co2FeSi Heusler compound
2009
Using Brillouin light scattering spectroscopy, we determine the spin-wave exchange stiffness D and the exchange constant A for thin films of the full Heusler compound Co2FeSi prepared by pulsed laser deposition. The thermal spin-wave spectra were measured in various magnetic fields, for different transferred spin-wave momenta, and for different film thicknesses. Fitting the observed spin-wave frequencies, we find an extraordinarily large value of
Study of the Spin Wave Linewidth in a 1-D Easy-Plane Ferromagnet Using Neutron Polarization Analysis
1990
An anomalous wavevector dependence in the spin wave linewidth associated with fluctuations out of the easy plane is observed for the first time in the one-dimensional easy-plane ferromagnet CsNiF3 by means of inelastic polarized neutron scattering. The linewidths of the spin waves, one attributed to spin fluctuations out of the easy plane and another in the easy plane, are studied separately throughout the Brillouin zone. The zone boundary narrowing of the linewidth associated with the spin fluctuations in the easy plane is observed for the first time in agreement with the classical spin wave theory. The deviations from the classical result at large qc and high temperature are interpreted a…
Magnetic excitations of a doped two-dimensional antiferromagnet
1993
Magnetic excitations of the two-dimensional (2D) t-J model are considered in the presence of a small concentration of holes c. The spin-wave approximation used implies long-range antiferromagnetic ordering from the beginning. Migdal's theorem is shown to be valid for the model considered. The energy spectrum of the magnons is determined with the help of the one-pole approximation for the hole Green's function. If the concentration of mobile holes is larger than a critical value an additional branch of overdamped magnons arises near the \ensuremath{\Gamma} and M points of the Brillouin zone. This is connected with the generation of electron-hole pairs (the Stoner excitations) by magnons. The…
Time-resolved imaging of pulse-induced magnetization reversal with a microwave assist field
2015
AbstractThe reversal of the magnetization under the influence of a field pulse has been previously predicted to be an incoherent process with several competing phenomena such as domain wall relaxation, spin wave-mediated instability regions and vortex-core mediated reversal dynamics. However, there has been no study on the direct observation of the switching process with the aid of a microwave signal input. We report a time-resolved imaging study of magnetization reversal in patterned magnetic structures under the influence of a field pulse with microwave assistance. The microwave frequency is varied to demonstrate the effect of resonant microwave-assisted switching. We observe that the swi…
Investigation of Feshbach resonances in ultracold K40 spin mixtures
2017
Magnetically tunable Feshbach resonances are an indispensable tool for experiments with atomic quantum gases. We report on 37 thus far unpublished Feshbach resonances and four further probable Feshbach resonances in spin mixtures of ultracold fermionic $^{40}\mathrm{K}$ with temperatures well below 100 nK. In particular, we locate a broad resonance at $B=389.7\phantom{\rule{0.16em}{0ex}}\text{G}$ with a magnetic width of $26.7\phantom{\rule{0.28em}{0ex}}\text{G}$. Here $1\phantom{\rule{0.28em}{0ex}}\text{G}={10}^{\ensuremath{-}4}\phantom{\rule{0.16em}{0ex}}\text{T}$. Furthermore, by exciting low-energy spin waves, we demonstrate a means to precisely determine the zero crossing of the scatte…
Spin-Wave Driven Bidirectional Domain Wall Motion in Kagome Antiferromagnets
2021
We predict a mechanism to controllably manipulate domain walls in kagome antiferromagnets via a single linearly polarized spin-wave source. We show by means of atomistic spin dynamics simulations of antiferromagnets with kagome structure that the speed and direction of the domain wall motion can be regulated by only tuning the frequency of the applied spin-wave. Starting from microscopics, we establish an effective action and derive the corresponding equations of motion for the spin-wave-driven domain wall. Our analytical calculations reveal that the coupling of two spin-wave modes inside the domain wall explains the frequency-dependent velocity of the spin texture. Such a highly tunable sp…
The VN2 negatively charged defect in diamond. A quantum mechanical investigation of the EPR response
2020
Abstract The VN 2 − defect in diamond consists of a vacancy surrounded by two substitutional nitrogen atoms, which lower the local symmetry from Td to C2v. Calculations of the doublet ground state geometry, electronic structure, EPR parameters, and IR spectra of this defect are reported along with a preliminary investigation of the observed optical transition. For the most part our results were obtained using a uniform charge compensated supercell approach together with the B3LYP functional and all-electron Gaussian basis sets designed for the properties studied. In particular, the computed hyperfine and quadrupolar EPR parameters for the carbon and nitrogen atoms adjacent to the vacancy ag…
Quantum gap and spin-wave excitations in the Kitaev model on a triangular lattice
2017
We study the effects of quantum fluctuations on the dynamical generation of a gap and on the evolution of the spin-wave spectra of a frustrated magnet on a triangular lattice with bond-dependent Ising couplings, analog of the Kitaev honeycomb model. The quantum fluctuations lift the subextensive degeneracy of the classical ground-state manifold by a quantum order-by-disorder mechanism. Nearest-neighbor chains remain decoupled and the surviving discrete degeneracy of the ground state is protected by a hidden model symmetry. We show how the four-spin interaction, emergent from the fluctuations, generates a spin gap shifting the nodal lines of the linear spin-wave spectrum to finite energies.
古典波動現象のトポロジーによる特徴付け; 静磁スピン波表面モードのトポロジカルな起源
2019
We propose a topological characterization of Hamiltonians describing classical waves. Applying it to the magnetostatic surface spin waves that are important in spintronics applications, we settle the speculation over their topological origin. For a class of classical systems that includes spin waves driven by dipole-dipole interactions, we show that the topology is characterized by vortex lines in the Brillouin zone in such a way that the symplectic structure of Hamiltonian mechanics plays an essential role. We define winding numbers around these vortex lines and identify them to be the bulk topological invariants for a class of semimetals. Exploiting the bulk-edge correspondence appropriat…