(a) Setup with the source grating , the phase grating , the analyzer absorption grating , and an electromagnet creating a horizontal variable magnetic field around the sample. (b) Multiple refraction of neutrons at magnetic domain walls in the sample causes a local degradation of the coherence of the neutron wave field and results in a decrease of the local fringe visibility of the interference pattern.
Neutron DFIs of the geometry-dependent magnetization process of the polycrystalline steel plate for different orientations , 22.5°, and 45°. Different magnetization behaviors and starting points of the propagation of the volume magnetization for each orientation are observed. The yellow color in the DFIs indicates domain wall-rich areas.
SANS results of the poly-crystalline steel plate for the and 45° orientations and a -field ramp from 0 to 250 mT. In 0 field configuration , for both orientations an isotropic scattering pattern is observed indicating a random domain wall orientation. A collapse of both SANS patterns between to is seen. For further increase of the magnetic field the scattering disappears and the original circular beam profile is finally regained at .
Comparison of the SANS measurement (red line) for the steel plate at 0° (squared markers) and 45° (diamond markers) and integrated DFI signal (blue lines) as a function of the external magnetic field from . The averaged DFI values are obtained by averaging over image values in a central region of . The SANS values represent the width ( -value) of corresponding Gaussian fits.
FEM simulation results for the , 22.5°, and 45° orientations of the steel plate and external field values of . White areas in the simulation are associated with Mode II , where the external field penetrates the sample and no more domain walls are present and no scattering of neutrons is present.
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