Speeding up nanomagnetic logic by DMI enhanced Pt/Co/Ir films

We investigated a new type of multilayer film for Nanomagnetic Logic with perpendicular anisotropy (pNML) enhanced by the Dzyaloshinskii-Moriya interaction (DMI). The DMI effect provides an additional energy term and widens the design space for pNML film optimization. In this work we added an Ir layer between Co and Pt to our standard pNML multilayer (ML) film stack - [Co/Pt]_x4. Multilayer stacks of films with and w/o Ir were sputtered and patterned to nanowires of 400 nm width by means of focused ion beam lithography (FIB). For comparability of the films they were tuned to show identical anisotropy for multilayer stacks with and w/o Ir. The field-driven domain wall (DW) velocity in the nanowires was measured by using wide-field MOKE microscopy. We found a strong impact of Ir on the DW velocity being up to 2 times higher compared to the standard [Co/Pt]_x4 ML films. Moreover, the maximum velocity is reached at much lower magnetic field, which is beneficial for pNML operation. These results pave the way for pNML with higher clocking rates and at the same time allow a further reduce power consumption.