Radiography of weakly ferromagnetic metals with polarized neutrons

The depolarization of a neutron beam passing through a ferromagnet crucially depends on the magnetic properties of the sample. Combining neutron depolarisation measurements with neutron radiography allows obtaining spatially resolved information about these properties. For measuring the depolarization, we have installed a longitudinal polarized beam setup at the ANTARES beamline consisting of 3He polarizers and flat coil spin flippers. With this setup we have performed radiography with polarized neutrons in the weak itinerant ferromagnets Pd1-xNix in order to determine the spatial distribution of the Curie temperatures TC in the samples. The results show that the single crystals are rather inhomogeneous showing large variations in TC. The data allows firstly to cut out small crystals with improved homogeneity for neutron scattering experiments and secondly to provide feedback for improving the growth techniques for the crystals. In the future we hope to use the potential of this method to map out magnetic domains across large volume samples.