# Non-van der Waals honeycomb antiferromagnet SrRu$_2$O$_6$ down to a few layers

## TL;DR

This paper reports the synthesis and characterization of ultra-thin SrRu$_2$O$_6$ sheets, a 4$d$ oxide with strong correlations and spin-orbit coupling, demonstrating that antiferromagnetism persists down to a few layers, opening new avenues for 2D magnetic materials.

## Contribution

It introduces a new 2D magnetic platform based on SrRu$_2$O$_6$, showing antiferromagnetism survives in ultra-thin layers and providing insights into its structural and magnetic properties.

## Key findings

- Antiferromagnetism persists in 3-5 monolayer SrRu$_2$O$_6$ sheets.
- Exfoliation occurs along planes perpendicular to the c-axis.
- Stacking and interlayer spacing influence magnetic properties.

## Abstract

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.