  Despite the considerable interest for antiferromagnets which appeared with
the perspective of using them for spintronics, their experimental study,
including the imaging of antiferromagnetic textures, remains a challenge. To
address this issue, quantum sensors, and in particular the nitrogen-vacancy
(NV) defects in diamond have become a widespread technical solution. We review
here the recent applications of single NV centers to study a large variety of
antiferromagnetic materials, from quantitative imaging of antiferromagnetic
domains and non-collinear states, to the detection of spin waves confined in
antiferromagnetic textures and the non-perturbative measurement of spin
transport properties. We conclude with recent developments improving further
the magnetic sensitivity of scanning NV microscopy, opening the way to detailed
investigations of the internal texture of antiferromagnetic objects.
