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II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
Two-dimensional (2D) magnets consist of a single or a few layers of ultimately thin magnetically ordered materials, of which the layers are separated by van der Waals gaps. Their discovery in 2017 came with a bit of surprise, since the Mermin-Wagner theorem seemed to prohibit their existence. Current research on 2D magnets is intense, as they are not only just a new class of magnets, but offer new physics since their magnetic state can be tuned by electric fields, light, or strain. 2D antiferromagnets are especially interesting, since antiferromagnets offer up to 1000 times faster switching compared to ferromagnets and lack a stray field. They provide a perspective of ultimate miniaturization in spintronics. After an introduction to the topic, this talk will show how 2D magnets
can be created that cannot be derived from a bulk crystal. For two of these 2D antiferromagnets, Cr2S3-2D and h-Fe2S2, it will be shown how the switching of 2D antiferromagnets can be detected, how the magnetic properties can be tuned by an electric field, and how the spin structure of such materials can be uncovered down to the atomic scale. This is accomplished by spin-polarized scanning tunneling microscopy in combination with x-ray circular magnetic dichroism and density functional theory calculations.