![]() ![]() Michels, Andreas ![]() Scientific Conference (2016, June 08) Detailed reference viewed: 61 (8 UL)![]() ![]() Michels, Andreas ![]() Scientific Conference (2016, April 26) Detailed reference viewed: 54 (9 UL)![]() ![]() Mettus, Denis ![]() ![]() Scientific Conference (2016, March 08) Bulk metallic glasses (BMG) are amorphous solids which are very well known for their excellent mechanical properties. In this contribution, we focus on their magnetic behavior and we discuss the influence ... [more ▼] Bulk metallic glasses (BMG) are amorphous solids which are very well known for their excellent mechanical properties. In this contribution, we focus on their magnetic behavior and we discuss the influence of mechanical deformation on the magnetic microstructure as seen by magnetic-field-dependent small-angle neutron scattering (SANS). This technique allows one to investigate the spin distribution in the bulk of the material and on the nanometer length scale. We present and compare the results of unpolarized SANS on various BMG samples (as-cast, aged, deformed) and we analyze the SANS cross section in real space by computing the correlation function. [less ▲] Detailed reference viewed: 114 (12 UL)![]() Michels, Andreas ![]() Presentation (2016, February 09) Detailed reference viewed: 61 (11 UL)![]() ; Mettus, Denis ![]() in Journal of Alloys & Compounds (2016), 661 Detailed reference viewed: 120 (10 UL)![]() ; Titov, Ivan ![]() in Journal of Alloys & Compounds (2016), 677 Detailed reference viewed: 105 (1 UL)![]() ; Kaiser, Daniel ![]() in Journal of Applied Crystallography (2016), 49 Detailed reference viewed: 121 (3 UL)![]() ; ; et al in Applied Surface Science (2016), 389 Detailed reference viewed: 131 (2 UL)![]() ; Michels, Andreas ![]() in Scientific Reports (2016), 6 Using analytical expressions for the magnetization textures of thin submicron-sized magnetic cylinders in vortex state, we derive closed-form algebraic expressions for the ensuing small-angle neutron ... [more ▼] Using analytical expressions for the magnetization textures of thin submicron-sized magnetic cylinders in vortex state, we derive closed-form algebraic expressions for the ensuing small-angle neutron scattering (SANS) cross sections. Specifically, for the perpendicular and parallel scattering geometries, we have computed the cross sections for the case of small vortex-center displacements without formation of magnetic charges on the side faces of the cylinder. The results represent a significant qualitative and quantitative step forward in SANS-data analysis on isolated magnetic nanoparticle systems, which are commonly assumed to be homogeneously or stepwise-homogeneously magnetized. We suggest a way to extract the fine details of the magnetic vortex structure during the magnetization process from the SANS measurements in order to help resolving the long-standing question of the magnetic vortex displacement mode. [less ▲] Detailed reference viewed: 131 (7 UL)![]() Michels, Andreas ![]() Presentation (2015, December 14) Detailed reference viewed: 34 (1 UL)![]() ![]() Michels, Andreas ![]() Scientific Conference (2015, September 14) Detailed reference viewed: 43 (3 UL)![]() ; Günther, Annegret ![]() ![]() in Nanoscale (2015), 7 The response of a colloidal dispersion of Ni nanorods to an oscillating magnetic field was characterized by optical transmission measurements as well as small-angle neutron scattering (SANS) experiments ... [more ▼] The response of a colloidal dispersion of Ni nanorods to an oscillating magnetic field was characterized by optical transmission measurements as well as small-angle neutron scattering (SANS) experiments using the TISANE (Time-dependent SANS experiments) technique. Exposed to a static magnetic field, the scattering intensity of the rod ensemble could be well described by the cylinder form factor using the geometrical particle parameters (length, diameter, orientation distribution) determined by transmission electronmicroscopy and magnetometry. An oscillation of the field vector resulted in a reorientation of the nanorods and a time-dependency of the scattering intensity due to the shape anisotropy of the rods. Analysis of the SANS data revealed that in the range of low frequencies the orientation distribution of the rods is comparable to the static case. With increasing frequency, the rod oscillation was gradually damped due to an increase of the viscous drag. It could be shown that despite of the increased friction in the high frequency range no observable change of the orientation distribution of the ensemble with respect to its symmetry axis occurs. [less ▲] Detailed reference viewed: 112 (9 UL)![]() ![]() Mettus, Denis ![]() ![]() Poster (2015, September 02) We present model calculations, based on the continuum theory of micromagnetics, for the correlation function of the spin-misalignment SANS cross section of bulk ferromagnets (e.g. elemental ... [more ▼] We present model calculations, based on the continuum theory of micromagnetics, for the correlation function of the spin-misalignment SANS cross section of bulk ferromagnets (e.g. elemental polycrystalline ferromagnets, soft and hard magnetic nanocomposites, nanoporous ferromagnets, or magnetic steels). For such materials, the spin disorder which is related to spatial variations in the saturation magnetization and magnetic anisotropy field results in strong spin-misalignment scattering dΣM/dΩ along the forward direction [1]. When the applied magnetic field is perpendicular to the incoming neutron beam, the characteristics of dΣM/dΩ (e.g. the angular anisotropy on a two-dimensional detector or the asymptotic power-law exponent) are determined by the ratio of magnetic anisotropy-field strength Hp to the jump ΔM in the saturation magnetization at internal interfaces. Here, we analyze the corresponding one and two-dimensional real-space correlations as a function of applied magnetic field, ratio Hp/ΔM, single-particle form factor, and particle volume fraction. Finally, we compare the theoretical results for the correlation function to experimental data on a Nd-Fe-B-based nanocomposite. [less ▲] Detailed reference viewed: 62 (2 UL)![]() ![]() Michels, Andreas ![]() Scientific Conference (2015, September) Detailed reference viewed: 41 (4 UL)![]() ![]() Michels, Andreas ![]() Poster (2015, September) Detailed reference viewed: 48 (2 UL)![]() ; ; Michels, Andreas ![]() in Physical Review. B : Condensed Matter (2015), 92(1), 014427 In inhomogeneous bulk ferromagnets, the dominating sources of spin disorder are related to spatial variations of (i) the magnitude of the local saturation magnetization and of (ii) the magnitude and/or ... [more ▼] In inhomogeneous bulk ferromagnets, the dominating sources of spin disorder are related to spatial variations of (i) the magnitude of the local saturation magnetization and of (ii) the magnitude and/or direction of the magnetic anisotropy field. For the particular example of a porous ferromagnet, where the magnetization inhomogeneity is at maximum, we demonstrate, by means of experimental neutron scattering data and micromagnetic simulations, the anisotropic character of magnetization fluctuations induced by the dipolar interaction. [less ▲] Detailed reference viewed: 58 (1 UL)![]() Michels, Andreas ![]() in Physical Review Letters (2015), (114), 149701 Detailed reference viewed: 126 (3 UL)![]() ; ; et al in Journal of Applied Physics (2015), 117 Detailed reference viewed: 121 (10 UL)![]() Perigo, Elio Alberto ![]() ![]() in Acta Materialia (2015), 87 Detailed reference viewed: 142 (12 UL)![]() ; Michels, Andreas ![]() in Physical Review. B, Condensed Matter and Materials Physics (2015), 91 Detailed reference viewed: 149 (11 UL) |
||