Spin-Polarized Current Switching of Co/Cu/Py Elongated Pac-Man Spin-Valve

We investigated spin-polarized current switching of elongated Pac-man (EPM) elements in a Pac-man shaped spin valve (Co/Cu/Py). The aspect ratio, pulse duration, and effect of antiferromagnetic (AFM) layer were simulated to obtain coherent switching. Pulse duration was varied on the picosecond (ps) scale and showed that ultra-fast switching could be achieved. A critical aspect ratio of 4.2 was found, where a minimum current density was observed. For antiparallel to parallel (AP-P) switching, a vortex formed during the switching process for aspect ratios less than 7. Aspect ratios of 7 or higher did not form a vortex and showed similar current densities to parallel to antiparallel (P-AP) switching as a result. It was found that the AFM layer prevented the formation of a vortex at the critical aspect ratio of 4.2 and effectively changed the switching mechanism. This allowed coherent switching with current densities for AP-P and P-AP to be only 7% from each other at the aspect ratio of 4.2.