  Imaging the magnetic structure of a material is essential to understanding
the influence of the physical and chemical microstructure on its magnetic
properties. Magnetic imaging techniques, however, have up to now been unable to
probe 3D micrometer-sized systems with nanoscale resolution. Here we present
the imaging of the magnetic domain configuration of a micrometre-thick FeGd
multilayer with hard X-ray dichroic ptychography at energies spanning both the
Gd L3 edge and the Fe K edge, providing a high spatial resolution spectroscopic
analysis of the complex X-ray magnetic circular dichroism. With a spatial
resolution reaching 45 nm, this advance in hard X-ray magnetic imaging is the
first step towards the investigation of buried magnetic structures and extended
three-dimensional magnetic systems at the nanoscale.
