Preparation of domain walls in Co/Pt multilayer wires

Current-induced domain wall motion for systematic studies of spin momentum transfer requires the reliable preparation of domain walls. Since high current densities can change or destroy the structures investigated, weak pinning potentials allowing the controlled and reliable depinning of domain walls at low current densities are desirable. A prerequisite for the preparation of a domain wall at such pinning sites is, that the domain wall nucleates at fields smaller than the field required to depin the domain wall. We suggest methods to tune the nucleation field of lithographically patterned Co/Pt multilayer wires. An up to fourfold reduction of the nucleation field could be achieved through altering the lateral shape of the wires or by depositing iron stripes on top. Furthermore we explored the applicability of geometric constrictions and ion implantation for the creation of pinning sites. The magnetization reversal of the structures was imaged by transmission X-ray microscopy at the Advanced Light Source in Berkeley, CA, USA. The authors gratefully acknowledge financial support by the Deutsche Forschungsgemeinschaft via SFB 668 and GrK 1286 as well as by the DOE.