Magnetic Scattering studies of rare earth thin film spiral antiferromagnetics

Understanding complex magnetic interactions by studying mesoscale magnetism creates and enhances technological applications. Holmium (Ho) is a rare-earth magnetic element with high magnetic moment per atom, and in bulk exhibits exotic magnetic properties such as a spiral antiferromagnetic state, the formation of chiral domains, or Spin-Slips.
In our study using X-ray magnetic resonant scattering we successfully detected the formation of antiferromagnetic spiral domains in thin film Ho by measuring magnetic satellite peaks around out-of-plane Ho Bragg peaks. Layers of Ho down to 100 nm are epitaxially grown on differently oriented MgO substrates (100), (110), (111) with an additional W seed layer using magnetron sputtering. Temperature dependent measurements of the transitions between ferromagnetic, antiferromagnetic, and paramagnetic state reveal a hysteresis in both the magnetic satellite peak and the thermal expansion of Ho. Furthermore, the width and amplitude of the hysteresis also depend on the Ho layer thickness, and even more pronounced, on the orientation of the MgO substrate. This shows a strong bottom interface dependency between the W layer and the structure and magnetic behavior of Ho, and, in general, the influence of the atomic structure on magnetism itself.