Optical Characterization of All-Magnetic NOT Gate Operation in Vortex Rings

We have demonstrated deterministic operation of inverters (NOT gates) using vortex magnetization states in pairs of linked 5 mum diameter permalloy rings with a small region of overlap. The input ring is clipped so that the state can be controlled by global fields, and is designed to switch at lower fields than the unclipped output ring, which then inverts the logical state of the input. Optical coatings over half of each ring provide distinct magnetooptic Kerr effect (MOKE) signatures for saturation, clockwise, and counterclockwise states in our focused beam system. We demonstrate that excessive overlap between the rings leads to overall shape anisotropy dominating the behavior of the structure.