Non-volatile skyrmion synapse and thresholded skyrmion activation device in a synthetic antiferromagnet Two neuromorphic devices in a synthetic-antiferromagnetic skyrmion multilayer. A synapse stores an analog weight as the diameter of a pinned skyrmion under a magnetic tunnel junction, set non-volatilely by the remanent polarisation of a ferroelectric gate. An activation device counts skyrmions admitted to a tapered chamber, fires one through a dimensioned constriction at a threshold population, leaks through an open input aperture and resets by subtraction.