Strong driving of a single coherent spin by a proximal chiral ferromagnet

We experimentally investigate the influence of a driven, dynamic vortex magnetization state on an individual nitrogen-vacancy (NV) spin in diamond. The vortex core can be translated within the ferromagnet using an applied magnetic field, allowing us to map out the spatial dependence of the interaction. The vortex displacement is determined usingmagneto-optical microscopy, while the vortex's influence on the spin is probed using optically detected magnetic resonance to measure the Rabioscillation frequency between spin levels. We find that the close proximity of the vortex core to the NV ( within about 200 nm) leads to more than an order of magnitude enhancement of the Rabi frequency. TheNV/vortex interaction differs significantly for transitions to the m(s) = + 1 and ms = - 1 spin states, which we attribute to the chiral nature of the vortex state dynamics. We compare the results with micromagnetic simulations and a simple analytical model to shed light on the mechanisms behind the observed effects.