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

Abstract

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.

Small-angle neutron scattering modeling of spin disorder in nanoparticles

“…Note that analytical micromagnetic calculations of the magnetic SANS cross section of nanoparticles are extremely difficult due to the nonlinear character of the underlying differential equations; a first attempt into this direction has been carried out by Metlov and Michels 34 , who computed the magnetic scattering related to vortices in thin submicron-sized soft ferromagnetic cylinders. Important aspects of computational micromagnetism are that (i) the parameter space can be relatively quickly scanned and that (ii) this methodology permits the investigation of the impact of the different interactions on magnetic SANS simply by switching on and off these interactions in simulations; such a procedure may then provide fundamental information on magnetic SANS.…”

Anomalous magnetic anisotropy and magnetic nanostructure in pure Fe induced by high-pressure torsion straining

“…To analyze the change in the magnetic domain size within nanosized regions, further improvement is necessary using micromagnetics. This method continues to progress with experimental, analytical, and micromagnetic-computational approaches [47][48][49]; the analytical solution for magnetic-field-dependent SANS intensity is only provided for a few special cases such as magnetic vortices in submicron-sized soft magnetic disks [48].…”

Effect of Dzyaloshinski-Moriya interaction on elastic small-angle neutron scattering

“…We would like to particularly emphasize that our interest is not directed towards the study of the skyrmion lattice, which is typically investigated by means of neutron diffraction at small scattering angles, 10 but to the microstructural-defect-induced impact of the DM interaction on the diffuse magnetic neutron scattering at small momentum transfers (q ∼ = 0). We take advantage of our recently developed micromagnetic SANS theory, [32][33][34][35] which considers magnetic small-angle scattering due to spatially fluctuating saturation magnetization and magnetic anisotropy fields. In addition to the standard magnetic energy contributions such as magnetostatics, magnetic anisotropy, and exchange (see below), we now consider also a phenomenological DM energy term [3][4][5]…”