  Harnessing the unique properties of non-collinear antiferromagnets (AFMs)
will be essential for exploiting the full potential of antiferromagnetic
spintronics. Indeed, many of the effects enabling ferromagnetic spintronic
devices have a corresponding counterpart in materials with non-collinear spin
structure. In addition, new phenomena such as the magnetic spin Hall effect
were experimentally observed in non-collinear AFMs, and the presence of the
equivalent to the ferromagnetic spin transfer torque via spin polarized
currents was theoretically predicted. In spite of these developments, an
interpretation of the rich physical phenomena observed in non-collinear
antiferromagnets is challenging, since the microscopic spin arrangement, the
magnetic domain distribution, and the domain orientations have proven
notoriously difficult to access experimentally. This is all the more
problematic, as imaging and writing magnetic domains is of central importance
for applications. Successful imaging is a basic requirement to experimentally
confirm the spin transfer torque acting on non-collinear domain walls and
therefore of eminent interest. Here, we demonstrate that the local magnetic
structure of the non-collinear AFM Mn3Sn films can be imaged by scanning
thermal gradient microscopy (STGM). The technique is based on scanning a laser
spot over the sample's surface, and recording the ensuing thermo-voltage. We
image the magnetic structure at a series of different temperatures and show
that at room temperature, the domain structure is not affected by the
application of moderate magnetic fields. In addition to imaging, we establish a
scheme for heat-assisted magnetic recording, using local laser heating in
combination with magnetic fields to intentionally write domain patterns into
the antiferromagnet.
