Noninvasive measurements of spin transport properties of an antiferromagnetic insulator.

Wang, Hailong; Zhang, Shu; McLaughlin, Nathan J; Flebus, Benedetta; Huang, Mengqi; Xiao, Yuxuan; Liu, Chuanpu; Wu, Mingzhong et al. · Sci Adv · 2022

basic_science · Level V

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Abstract

Antiferromagnetic insulators (AFIs) are of substantial interest because of their potential in the development of 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 noninvasive method to optically access the intrinsic spin transport properties of an archetypical AFI α-Fe<sub>2</sub>O<sub>3</sub> via nitrogen-vacancy (NV) quantum spin sensors. By NV relaxometry measurements, we successfully detect the frequency-dependent dynamic fluctuations of the spin density of α-Fe<sub>2</sub>O<sub>3</sub> along the Néel order parameter, from which an intrinsic spin diffusion constant of α-Fe<sub>2</sub>O<sub>3</sub> 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 such as two-dimensional magnets, spin liquids, and magnetic Weyl semimetals, which are challenging to access by the conventional measurement techniques.