Imaging of antiferromagnetic domains

Finding out that the elementary magnets in antiferromagnetic materials can be switched by applying an electric current has been a milestone for the use of antiferromagnets in spintronics (e.g., for extremely fast memory components). The antiferromagnetic order is characterized by the formation of domains. These domains have a well-defined magnetic orientation of the elementary magnets and a magneto-Seebeck coefficient that depends on the magnetization direction.

In collaboration with the University of Regensburg, a method has been developed to shed light on the local order of these domains. Switching domains using current pulses could be analyzed for the first time in the CuMnAs material system, which is particularly relevant for various applications. The method is based on atomic force microscopy (AFM). In order to measure the antiferromagnetic order, a metal-coated AFM tip is irradiated by an IR laser, which generates a very strong local temperature gradient. A voltage, which depends on the material, the temperature and the magnetization (magneto-Seebeck effect), occurs at this hot spot and is then measured. If the tip passes an area in which a domain is changing directions, this change is indicated by the measured voltage. Magneto-Seebeck microscopy can thus be used to characterize the antiferromagnetic order. This procedure was used to image not only the magnetic domains in a thin 20 nm antiferromagnetic layer of CuMnAs but also its manipulation by means of current pulses.

This new procedure for imaging antiferromagnetic domains with high spatial resolution will become an important instrument for future investigations of the fundamental physical properties of novel switching mechanisms, which are essential elements in the emerging field of antiferromagnetic spintronics.