Nitrogen-vacancy (NV) magnetometry

Nitrogen-vacancy magnetometry uses point defects in diamond, a nitrogen atom beside a lattice vacancy, whose electronic spin state can be initialised and read optically and whose fluorescence shifts with the local magnetic field. Because a diamond sensor can be made very small and operates at room temperature without the low-field, heated-vapour requirements of SERF OPMs, it offers a route to magnetic sensing very close to tissue, potentially at high spatial resolution.

For neural sensing NV magnetometry is early-stage: it has resolved the magnetic field of action potentials in excised invertebrate axons placed directly on a diamond sensor, but its sensitivity per unit volume is currently worse than SERF OPMs, so intact non-invasive human recording is not yet demonstrated. It is best understood as a promising magnetic contrast mechanism whose sensitivity, resolution, and proximity tradeoffs differ from OPMs, not as a deployed BCI sensor.