Spin-relaxation of Defect Center Qubit by Off-Resonant Pinned Domain Wall Oscillations

The nitrogen-vacancy (NV) center, a fluorescent defect in diamond, has emerged as a powerful room temperature quantum sensor for probing the local properties of ferromagnetic textures; for example, it has been used for static imaging of domain walls (DW) [Nat. Commun.6, 6733 (2015] and skyrmions [Nat Commun. 9, 2712 (2018)], as well as dynamic measurements of magnetic vortex gyrations [J. Appl. Phys., 130, 083903 (2021)]. Here, we demonstrate off-resonant spin relaxation of NV centers in deterministically placed nanodiamonds via the GHz-scale oscillations of a pinned DW. By placing the nanodiamonds over a pinning site determined by a notch in the wire and shape anisotropy, we reliably measure the spin dynamics of both a nucleated and denucleated control case. Then, we compare these results to micromagnetic simulations to further confirm our results. This work expands the menagerie of magnetization dynamics that can be detected with NV centers and builds the foundation for future DW qubit coupling experiments, presenting a powerful new avenue for local microwave driving and qubit addressability.