Figure 2: Resonant detection of driven spin-wave excitations.
From: Nanometre-scale probing of spin waves using single electron spins
(a), Measured Rabi frequency as a function of ESR frequency for three NV centres close to the disc (NVA, NVB and NVC, see Fig. 1b) and reference NV centre NVref far from the disc. We tune the NV ESR frequency using the external magnetic field Bext and drive Rabi oscillations by applying a MW magnetic field at the ESR frequency. The ESR frequency range below (above) 2.87 GHz corresponds to the ms=0↔−1 (ms=0↔+1) transition. (b), Ratio of the Rabi frequency of NVi (i=A,B,C) over the Rabi frequency of NVref, as measured in a. Pronounced resonances are visible where the NV centre ESR frequency matches the numerically calculated ferromagnetic resonance (FMR) of the disc, which occurs at the vertical dashed lines (see c). The grey inset depicts the interference between the a.c. magnetic field generated by a spin-wave excitation 
at the site of NVi (i=A,B,C) and the driving field bD in a frame rotating at the NV centre ESR frequency. (c) Measured ESR frequencies and numerically calculated FMR frequency as a function of external magnetic field Bext.
