NV-Diamond Magnetometry in the NV-NV Interaction Limit

In nitrogen-vacancy (NV) ensembles in diamond, the magnetic sensitivity is commonly limited by a bath of other impurity spins, which decoheres the NV sensor spins. We demonstrate mitigation of NV-bath interactions by RF control of the spin bath or dynamical decoupling of the NV centers. In this regime, mutual NV-NV dipolar interactions dominate the ensemble spin properties (T2, T2*). These techniques may yield improved DC and AC magnetic sensitivity up to a limit set by NV-NV dipolar interactions. For example, we show NV ensemble coherence times under XY8-n dynamical decoupling protocols limited by instantaneous diffusion. We present progress toward mitigating NV-NV interactions while preserving magnetic sensitivity, and conversely we outline ideas to leverage strong NV-NV interactions to further improve magnetic sensitivity.