![]() Adams, Michael Philipp ![]() ![]() ![]() in IUCrJ (2023), 10(3), 261-269 The magnetic small-angle neutron scattering (SANS) cross section of dilute ensembles of uniformly magnetized and randomly oriented Stoner–Wohlfarth particles is calculated using the Landau–Lifshitz ... [more ▼] The magnetic small-angle neutron scattering (SANS) cross section of dilute ensembles of uniformly magnetized and randomly oriented Stoner–Wohlfarth particles is calculated using the Landau–Lifshitz equation. The focus of this study is on the angular anisotropy of the magnetic SANS signal as it can be seen on a two-dimensional position-sensitive detector. Depending on the symmetry of the magnetic anisotropy of the particles (e.g. uniaxial, cubic), an anisotropic magnetic SANS pattern may result, even in the remanent state or at the coercive field. The case of inhomogeneously magnetized particles and the effects of a particle-size distribution and interparticle correlations are also discussed. [less ▲] Detailed reference viewed: 29 (1 UL)![]() Sinaga, Evelyn Pratami ![]() ![]() ![]() in Physical Review. B (2023), 107 Detailed reference viewed: 82 (18 UL)![]() Adams, Michael Philipp ![]() ![]() in Journal of Applied Crystallography (2022), 55(6), 1488-1499 Detailed reference viewed: 22 (2 UL)![]() Adams, Michael Philipp ![]() ![]() in Journal of Applied Crystallography (2022), 55(6), 1475-1487 Detailed reference viewed: 24 (2 UL)![]() Malyeyev, Artem ![]() ![]() in Journal of Applied Crystallography (2022), 55 Based on Brown’s static equations of micromagnetics, the uniaxial polarization of the scattered neutron beam of a bulk magnetic material is computed. The approach considers a Hamiltonian that takes into ... [more ▼] Based on Brown’s static equations of micromagnetics, the uniaxial polarization of the scattered neutron beam of a bulk magnetic material is computed. The approach considers a Hamiltonian that takes into account the isotropic exchange interaction, the antisymmetric Dzyaloshinskii–Moriya interaction, magnetic anisotropy, the dipole–dipole interaction, as well as the effect of an applied magnetic field. In the high-field limit, the solutions for the magnetization Fourier components are used to obtain closed-form results for the spinpolarized SANS (small-angle neutron scattering) cross sections and the ensuing polarization. The theoretical expressions are compared with experimental data on a soft magnetic nanocrystalline alloy. The micromagnetic SANS theory provides a general framework for polarized real-space neutron methods, and it may open up a new avenue for magnetic neutron data analysis on magnetic microstructures. [less ▲] Detailed reference viewed: 53 (5 UL)![]() ![]() Estupinan Donoso, Alvaro Antonio ![]() ![]() ![]() Scientific Conference (2022, May 31) During the Discrete Element Method (DEM) representation of powder bed processes (e.g. tungsten oxide reduction, tungsten carbide synthesis, selective laser sintering) a numerical solution for each single ... [more ▼] During the Discrete Element Method (DEM) representation of powder bed processes (e.g. tungsten oxide reduction, tungsten carbide synthesis, selective laser sintering) a numerical solution for each single particle is impractical due to the extremely high number of particles (e.g. 10^12). However, in such processes, particles in the vicinity of each other observe low gradients concerning their thermodynamic state. This characteristic can be exploited to avoid solving repeatedly numerically equivalent equation systems. This contribution presents two numerical methods aiming to reduce the computational costs of DEM approaches for the thermochemical conversion of powder beds. In the two methods after an appropriated numerical treatment, a group of particles under similar boundary conditions is substituted by a single-effective-entity. Consequently, the entire powder space is divided into sub-domains to be solved. The methods result in considerable lower number of equations that increase computational efficiency and enable feasible time simulations. The applications of the industrial synthesis of tungsten powders and the selective laser sintering (SLS) of powder metals are presented and discussed. [less ▲] Detailed reference viewed: 44 (2 UL)![]() Bersweiler, Mathias ![]() ![]() ![]() in Neutron News (2022), 33(2), 15-17 Detailed reference viewed: 33 (2 UL)![]() ; Bersweiler, Mathias ![]() in Nanoscale Advances (2022), 4 Detailed reference viewed: 45 (3 UL)![]() Bersweiler, Mathias ![]() ![]() ![]() in IUCrJ (2022), 9(1), 65-72 Detailed reference viewed: 71 (11 UL)![]() Adams, Michael Philipp ![]() ![]() in Journal of Applied Crystallography (2022), 55 Detailed reference viewed: 58 (5 UL)![]() Bersweiler, Mathias ![]() ![]() in Journal of Applied Crystallography (2022), 55 Detailed reference viewed: 58 (4 UL)![]() ; ; Michels, Andreas ![]() in Journal of Applied Crystallography (2022), 55 Detailed reference viewed: 35 (3 UL)![]() ; ; et al in Scientific Reports (2022), 12 Detailed reference viewed: 26 (0 UL)![]() Haller, Andreas ![]() E-print/Working paper (2021) Skyrmions are topological magnetic textures which can arise in non-centrosymmetric ferromagnetic materials. In most systems experimentally investigated to date, skyrmions emerge as classical objects ... [more ▼] Skyrmions are topological magnetic textures which can arise in non-centrosymmetric ferromagnetic materials. In most systems experimentally investigated to date, skyrmions emerge as classical objects. However, the discovery of skyrmions with nanometer length scales has sparked interest in their quantum properties. Quantum corrections to the classical magnetic textures have already been considered in the semiclassical regime. Here, we go beyond this limit by investigating quantum skyrmions in the deep quantum regime. We use density matrix renormalization group techniques to study two-dimensional spin-1/2 Heisenberg ferromagnets with Dzyaloshinskii-Moriya interactions and discover a broad region in the zero temperature phase diagram which hosts quantum skyrmion lattice ground states. We argue that this novel quantum skyrmion phase can be detected experimentally in the magnetization profile via local magnetic polarization measurements as well as in the spin structure factor measurable via neutron scattering experiments. Finally, we explore the resulting quantum skyrmion state, analyze its real space polarization profile and show that it is a non-classical state featuring entanglement between quasiparticle and environment mainly localized near the boundary spins of the skyrmion. [less ▲] Detailed reference viewed: 49 (10 UL)![]() Bersweiler, Mathias ![]() ![]() Scientific Conference (2021, October 16) Detailed reference viewed: 47 (2 UL)![]() ; Bersweiler, Mathias ![]() in Physical Review Materials (2021), 5 Detailed reference viewed: 29 (0 UL)![]() Bersweiler, Mathias ![]() ![]() ![]() in Physical Review Materials (2021), 5(4), 044409 Detailed reference viewed: 110 (29 UL)![]() Malyeyev, Artem ![]() in Physical Review Materials (2021), 5 We report the results of an unpolarized small-angle neutron scattering (SANS) study on Mn-Bi-based rare-earth-free permanent magnets. The magnetic SANS cross section is dominated by long-wavelength ... [more ▼] We report the results of an unpolarized small-angle neutron scattering (SANS) study on Mn-Bi-based rare-earth-free permanent magnets. The magnetic SANS cross section is dominated by long-wavelength transversal magnetization fluctuations and has been analyzed in terms of the Guinier-Porod model and the distance distribution function. This provides the radius of gyration which, in the remanent state, ranges between about $220-240 \, \mathrm{nm}$ for the three different alloy compositions investigated. Moreover, computation of the distance distribution function in conjunction with results for the so-called $s$-parameter obtained from the Guinier-Porod model indicate that the magnetic scattering of a Mn$_{45}$Bi$_{55}$ sample has its origin in slightly shape-anisotropic structures. [less ▲] Detailed reference viewed: 86 (17 UL)![]() ; Malyeyev, Artem ![]() in Journal of Alloys and Compounds (2021), 890 Detailed reference viewed: 61 (8 UL)![]() ; ; et al in Physical Review. B, Condensed Matter (2021), 104 Detailed reference viewed: 47 (0 UL) |
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