  Nucleation of domain walls by current-driving a single domain wall, confined
to the junction area of two symmetrical strips, is investigated using
systematic micromagnetic simulations. Secondary domain walls (equivalently,
bits encoded in domains) are simultaneously nucleated and driven by
alternatively applying current pulses between two terminals in the structure.
Simulations show that nanosecond-duration current pulses nucleate and drive
series of robust up/down domains even under realistic conditions. These results
demonstrate a technique for sequentially nucleating and shifting domain walls
without using attached external bit lines, fields or modifying the
ferromagnetic strip.
