  We demonstrate from both simulation and experiment a simple scheme for
selective injection of multiple domain walls in a magnetic nanowire. The
structure consists of a side-contact misaligned Hall bar made of
ferromagnet/heavy metal bilayers. The combination of current-induced spin-orbit
torque and an external magnetic field allows for the formation of localized
domains with specific magnetization direction and length, thereby creating
domain walls in predetermined locations. With the side contacts at two sides
misaligned for a distance that is comparable to the contact width, it is
possible to create densely packed domains by simply applying current between
different pairs of side contacts. Simulation results show that the proposed
scheme is scalable to a large number of domains with its dimension limited only
by the domain wall width.
