  The current family of experimentally realized two-dimensional magnetic
materials consist of 3$d$ transition metals with very weak spin-orbit coupling.
In contrast, we report a new platform in a chemically bonded and layered 4$d$
oxide, with strong electron correlations and competing spin-orbit coupling. We
synthesize ultra-thin sheets of SrRu$_2$O$_6$ using scalable liquid
exfoliation. These exfoliated sheets are characterized by complementary
experimental and theoretical techniques. The thickness of the nano-sheets
varies between three to five monolayers, and within the first-principles
calculations, we show that antiferromagnetism survives in these ultra-thin
layers. Experimental data suggest that exfoliation occurs from the planes
perpendicular to the $c$-axis as the intervening hexagonal Sr-lattice separates
the two-dimensional magnetic honeycomb Ru-layers. The high-resolution
transmission electron microscope images indicate that the average inter-atomic
spacing between the Ru-layers is slightly reduced, which agrees with the
present calculations. The signatures of rotational stacking of the nanosheets
are also observed. Such new two-dimensional platform offers enormous
possibilities to explore emergent properties that appear due to the interplay
between magnetism, strong correlations and spin-orbit coupling. Moreover, these
effects can be further tuned as a function of layer thickness.
