scholarly journals Small-angle neutron scattering correlation functions of bulk magnetic materials

2015 ◽  
Vol 48 (5) ◽  
pp. 1437-1450 ◽  
Author(s):  
Denis Mettus ◽  
Andreas Michels
Keyword(s):  
Magnetic Field ◽  
Correlation Function ◽  
Magnetic Anisotropy ◽  
Neutron Scattering ◽  
Saturation Magnetization ◽  
Applied Magnetic Field ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Anisotropy Field ◽  
Two Dimensional

On the basis of the continuum theory of micromagnetics, the correlation function of the spin-misalignment small-angle neutron scattering cross section of bulk ferromagnets (e.g.elemental polycrystalline ferromagnets, soft and hard magnetic nanocomposites, nanoporous ferromagnets, or magnetic steels) is computed. 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. 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 strengthHpto the jump ΔMin the saturation magnetization at internal interfaces. Here, the corresponding one- and two-dimensional real-space correlations are analyzed as a function of applied magnetic field, the ratioHp/ΔM, the single-particle form factor and the particle volume fraction. Finally, the theoretical results for the correlation function are compared with experimental data on nanocrystalline cobalt and nickel.

scholarly journals Feasibility of Probing the Filler Restructuring in Magnetoactive Elastomers by Ultra-Small-Angle Neutron Scattering

2021 ◽  
Vol 11 (10) ◽  
pp. 4470
Author(s):  
Inna A. Belyaeva ◽  
Jürgen Klepp ◽  
Hartmut Lemmel ◽  
Mikhail Shamonin
Keyword(s):  
Magnetic Field ◽  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Iron Particles ◽  
Filler Particles ◽  
The Magnetic Field ◽  
Magnetoactive Elastomer

Ultra-small-angle neutron scattering (USANS) experiments are reported on isotropic magnetoactive elastomer (MAE) samples with different concentrations of micrometer-sized iron particles in the presence of an in-plane magnetic field up to 350 mT. The effect of the magnetic field on the scattering curves is observed in the scattering vector range between 2.5 × 10−5 and 1.85 × 10−4 Å−1. It is found that the neutron scattering depends on the magnetization history (hysteresis). The relation of the observed changes to the magnetic-field-induced restructuring of the filler particles is discussed. The perspectives of employing USANS for investigations of the internal microstructure and its changes in magnetic field are considered.

Autocorrelation function of the spin misalignment in magnetic small-angle neutron scattering: application to nanocrystalline metals

2013 ◽  
Vol 46 (3) ◽  
pp. 788-790 ◽  
Author(s):  
Andreas Michels ◽  
Jens-Peter Bick
Keyword(s):  
Neutron Scattering ◽  
Autocorrelation Function ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Anisotropy Field ◽  
Real Space ◽  
Scattering Data ◽  
Stiffness Constant ◽  
The Mean ◽  
Cobalt And Nickel

Real-space magnetic small-angle neutron scattering data from nanocrystalline cobalt and nickel have been analysed in terms of a recently developed micromagnetic theory for the autocorrelation function of the spin misalignment [Michels (2010).Phys. Rev. B,82, 024433]. The approach provides information on the exchange-stiffness constant and on the mean magnetic `anisotropy-field' radius.

scholarly journals Magnetic field dependent small-angle neutron scattering on a Co nanorod array: evidence for intraparticle spin misalignment

2014 ◽  
Vol 47 (3) ◽  
pp. 992-998 ◽  
Author(s):  
A. Günther ◽  
J.-P. Bick ◽  
P. Szary ◽  
D. Honecker ◽  
C. D. Dewhurst ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Neutron Scattering ◽  
Cross Section ◽  
Field Dependence ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Strong Field ◽  
Structural Parameters ◽  
Nanorod Array ◽  
Field Dependent

The structural and magnetic properties of a cobalt nanorod array have been studied by means of magnetic field dependent small-angle neutron scattering (SANS). Measurement of the unpolarized SANS cross section dΣ/dΩ of the saturated sample in the two scattering geometries where the applied magnetic fieldHis either perpendicular or parallel to the wavevectorkiof the incoming neutron beam allows one to separate nuclear from magnetic SANS, without employing the usual sector-averaging procedure. The analysis of the SANS data in the saturated state provides structural parameters (rod radius and centre-to-centre distance) that are in good agreement with results from electron microscopy. Between saturation and the coercive field, a strong field dependence of dΣ/dΩ is observed (in both geometries), which cannot be explained using the conventional expression of the magnetic SANS cross section of magnetic nanoparticles in a homogeneous nonmagnetic matrix. The origin of the strong field dependence of dΣ/dΩ is believed to be related to intradomain spin misalignment, due to magnetocrystalline and magnetoelastic anisotropies and magnetostatic stray fields.

scholarly journals Aligning self-assembled perylene bisimides in a magnetic field

2018 ◽  
Vol 54 (78) ◽  
pp. 10977-10980 ◽  
Author(s):  
Emily R. Draper ◽  
Matthew Wallace ◽  
Dirk Honecker ◽  
Dave J. Adams
Keyword(s):  
Magnetic Field ◽  
Thin Films ◽  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Electrochemical Techniques ◽  
Perylene Bisimide ◽  
Self Assembled ◽  
Perylene Bisimides

Directional dependent photoresponsive perylene bisimide thin films can be made by aligning and drying under a magnetic field. This can be monitored by NMR and small angle neutron scattering and assessed by imaging and electrochemical techniques.

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