Link to publication: http://advances.sciencemag.org/content/3/5/e1603137.full
The ability to sense the magnetic state of individual magnetic nano-objects is a key capability for powerful applications ranging fromreadout of ultradense magneticmemory to themeasurement of spins in complex structures with nanometer precision. Magnetic nano-objects require extremely sensitive sensors and detectionmethods. We create an atomic spin sensor consisting of three Fe atoms and show that it can detect nanoscale antiferromagnets through minute, surfacemediated magnetic interaction. Coupling, even to an object with no net spin and having vanishing dipolar stray field, modifies the transition matrix element between two spin states of the Fe atom–based spin sensor that changes the sensor’s spin relaxation time. The sensor can detect nanoscale antiferromagnets at up to a 3-nm distance and achieves an energy resolution of 10 meV, surpassing the thermal limit of conventional scanning probe spectroscopy. This scheme permits simultaneous sensing of multiple antiferromagnets with a single-spin sensor integrated onto the surface.