We experimentally demonstrate a simple and robust protocol for the detection of weak radio-frequency magnetic fields using a single electron spin in diamond. Our method relies on spin locking, where the Rabi frequency of the spin is adjusted to match the MHz signal frequency. In a proof-of-principle experiment we detect a 7.5 MHz magnetic probe field of 40 nT amplitude with <10 kHz spectral resolution over a T_1-limited noise floor of 0.3 nT/rtHz. Rotating-frame magnetometry may provide a direct and sensitive route to high-resolution spectroscopy of nanoscale nuclear spin signals.
@article{arxiv.1210.1443,
title = {Radio-frequency magnetometry using a single electron spin},
author = {M. Loretz and T. Rosskopf and C. L. Degen},
journal= {arXiv preprint arXiv:1210.1443},
year = {2013}
}