Influence of the domain wall nucleation time on the reliability of perpendicular Nanomagnetic Logic

In this paper, we show that the time for domain wall (DW) nucleation in a magnet with perpendicular magnetic anisotropy (PMA) has to be considered to ensure reliable computation in perpendicular Nanomagnetic Logic (pNML). A theoretical model for the time-dependent DW nucleation probability in field-coupled nanomagnets is applied. Conditions for reliable computation in pNML circuits are derived depending on the nucleation time, the applied clocking field and the coupling strength between the nanomagnets. In the experiments, the DW nucleation time is measured in 400 nm-wide magnetic nanowires using magneto-optical microscopy. The required field pulses in the 100 ns-range are generated by an on-chip coil. The field-dependent DW velocity in the magnetic nanowires is measured and the DW nucleation time is determined by experiment. The measurement results are compared to the theoretical model, which is calibrated by experimental data. Our results verify the presented model and pave the way for the further development of pNML circuitry.