Magnetic SANS on bulk ferromagnets

Scientific Conference (2016, June 08)

Magnetic small-angle neutron scattering on bulk metallic glasses

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 ▲]

Magnetic microstructure of a textured Nd-Fe-B sintered magnet characterized by small-angle neutron scattering

in Journal of Alloys & Compounds (2016), 661

Magnetic field-dependent spin structures of nanocrystalline holmium

in Journal of Applied Crystallography (2016), 49

Magnetic neutron scattering by magnetic vortices in thin submicron-sized soft ferromagnetic cylinders

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 ▲]

Anisotropic magnetic correlations in nanocomposites

Scientific Conference (2015, September 14)

Magnetic SANS correlation functions of bulk magnetic materials

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 ▲]

Magnetic small-angle neutron scattering: beyond the particle-matrix concept

Poster (2015, September)

Comment on “Origin of Surface Canting within Fe3O4 Nanoparticles”

in Physical Review Letters (2015), (114), 149701

Magnetic SANS study of a sintered Nd–Fe–B magnet: Estimation of defect size

in Acta Materialia (2015), 87