Antiferromagnetic insulators (AFIs) are of significant interest due to their potential to develop next-generation spintronic devices. One major effort in this emerging field is to harness AFIs for long-range spin information communication and storage. Here, we report a non-invasive method to optically access the intrinsic spin transport properties of an archetypical AFI {\alpha}-Fe2O3 via nitrogen-vacancy (NV) quantum spin sensors. By NV relaxometry measurements, we successfully detect the time-dependent fluctuations of the longitudinal spin density of {\alpha}-Fe2O3. The observed frequency dependence of the NV relaxation rate is in agreement with a theoretical model, from which an intrinsic spin diffusion constant of {\alpha}-Fe2O3 is experimentally measured in the absence of external spin biases. Our results highlight the significant opportunity offered by NV centers in diagnosing the underlying spin transport properties in a broad range of high-frequency magnetic materials, which are challenging to access by more conventional measurement techniques.
@article{arxiv.2011.03905,
title = {Quantum Sensing of Spin Transport Properties of an Antiferromagnetic Insulator},
author = {Hailong Wang and Shu Zhang and Nathan J. McLaughlin and Benedetta Flebus and Mengqi Huang and Yuxuan Xiao and Eric E. Fullerton and Yaroslav Tserkovnyak and Chunhui Rita Du},
journal= {arXiv preprint arXiv:2011.03905},
year = {2022}
}