  The knowledge of how the magnetization looks inside a ferromagnet is often
hindered by the limitations of the available experimental methods that are
sensitive only to the surface regions or limited in spatial resolution. We
report the 3D tomographic reconstruction of the magnetization within a
ferromagnetic film of 240 nm in thickness using soft X ray microscopy and
magnetic dichroism. The film has periodic magnetic domains forming stripes and
closure domains found to be shifted from the stripe array by 1/4 of the period.
In addition, the bifurcations of the stripes, which act as inversion nuclei of
the magnetization, evidence in 3D meron singularities and Bloch points at the
interior of the film. This novel method can be easily extended to magnetic
stacks in spintronics applications and other singularities in films.
