Deposition and patterning of magnetic atom trap lattices in FePt films with periods down to 200 nm

We report on the epitaxial growth and the characterization of thin FePt films and the subsequent patterning of magnetic lattice structures. These structures can be used to trap ultracold atoms for quantum simulation experiments. We use molecular beam epitaxy to deposit monocrystalline FePt films with a thickness of 50 nm. The films are characterized with X-ray scattering and Mössbauer spectroscopy to determine the long range order parameter and the hard magnetic axes. A high monocrystalline fraction was measured as well as a strong remanent magnetization of M = 900 kA/m and coercivity of 0.4 T. Using electron beam lithography and argon ion milling, we create lattice patterns with a period down to 200 nm, and a resolution of 30 nm. The resulting lattices are imaged in a scanning electron microscope in the cross-section created by a focused ion beam. A lattice with continuously varying lattice constant ranging from 5 μm down to 250 nm has been created to show the wide range of length scales that can now be created with this technique.