Detection of above-NV-frequency ferromagnetic dynamics*

The nitrogen vacancy (NV) spin in diamond can sense magnetic field noise at gigahertz frequencies due to its long spin lifetime and spin dependent fluorescence intensity. Thus far, NV sensing of ferromagnetic noise has had an upper frequency limit since NVs are relaxed by dipole fields from magnons at the NV frequency [1,2]. Here, we use microwaves to drive a low damping ferrite thin film and simultaneously detect conventional microwave absorption and NV fluorescence signals. Driving a spinwave instability in the ferrite film results in relaxation of nearby NV centers even when sufficient static field is applied to the film such that there are no NV-resonant magnon modes [3]. Recent theory [4] suggests that multiple magnons participate in producing NV-resonant magnetic field noise when the magnon population is elevated, which provides a pathway for high frequency magnetization dynamics sensing with NVs.

[1] Nat. Comm. 6, 7886 (2015)
[2] J. Appl. Phys. 126, 124902 (2019)
[3] Nat Comm. 11, 5229 (2020)
[4] Phys. Rev. Lett. 121, 187204 (2018)