Magnetic neutron scattering studies on Nd-Fe-B magnets

Presentation (2016, February 09)

Small-angle neutron scattering study of coercivity enhancement in grain-boundary-diffused Nd-Fe-B sintered magnets

in Journal of Alloys & Compounds (2016), 677

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 ▲]

Magnetic neutron scattering studies on Nd-Fe-B magnets

Presentation (2015, December 14)

Excitation of Ni nanorod colloids in oscillating magnetic fields: a new approach for nanosensing investigated by TISANE

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 ▲]

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

Poster (2015, September)

Dipolar spin-misalignment correlations in inhomogeneous magnets: Comparison between neutron scattering and micromagnetic

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 ▲]

Synthesis and magnetic properties of Ta/NdFeB-based composite microwires

in Journal of Applied Physics (2015), 117

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

Scientific Conference (2015)

Small-angle neutron scattering of nanocrystalline gadolinium and holmium with random paramagnetic susceptibility

in Journal of Physics : Condensed Matter (2015), 27