We performed spatially resolved imaging of ferromagnetic transitions in Ni₃Al and HgCr₂Se₄ crystals. These neutron depolarization measurements discovered bulk magnetic inhomogeneities in the ferromagnetic transition temperature with spatial resolution of about 100 µm. To obtain such spatial resolution, we employed a novel neutron microscope equipped with Wolter mirrors as a neutron image-forming lens and a focusing neutron guide as a neutron condenser lens. The images of Ni₃Al show that the sample does not homogeneously go through the ferromagnetic transition. The improved resolution allowed us to identify a distribution of small grains with slightly
off-stoichiometric composition. Additionally, neutron depolarization imaging experiments on the chrome spinel, HgCr₂Se₄, under high pressures up to 15 kbar highlight the advantages of the new technique especially for small samples or sample environments with restricted sample space as in high pressure experiments. The improved spatial resolution enables to observe domain formation in the sample while decreasing the acquisition time despite having a bulky pressure cell in the beam. The novel optical design that enabled acquisition of the high spatial resolution neutron depolarization images will be described in detail and image results are compared to a conventional radiography setup without a lens. Improvements in the Wolter mirror designs are expected to increase the spatial resolution to the micrometer range, bringing it a step closer to what is achieved with X-rays.

See recent publication: Jorba, Pau, et al. "High-resolution neutron depolarization microscopy of the ferromagnetic transitions in Ni₃Al and HgCr₂Se₄ under pressure." Journal of Magnetism and Magnetic Materials 475 (2019): 176-183.