Spin transport in antiferromagnetic insulators: progress and challenges

Spin transport is a key process in the operation of spin-based devices that has been the focus of spintronics research for the last two decades. Conductive materials, such as semiconductors and metals, in which the spin transport relies on electron diffusion, have been employed as the channels for spin transport in most studies. Due to the absence of conduction electrons, the potential to be a spin channel has long been neglected for insulators. However, since the demonstration of spin transmission through a ferromagnetic insulator, it was realized that insulators with magnetic ordering can also serve as channels for spin transport. Here, the recent progress of spin transport in antiferromagnetic insulators is briefly described with an introduction to the experimental techniques. The observations regarding the temperature dependence of spin transmission, spin current switching and the negative spin Hall magnetoresistance are discussed. We also include the challenges for developing the functionality of antiferromagnetic insulators as well as the unresolved problems from the experimental observations.