Atomically thin materials that are both magnetic and conductive offer great promise for applications in spintronics, where information can be stored and transferred via the manipulation of electron spin. However, finding a material that meets all the requisite criteria is a challenge. Transition-metal oxides circumvent many of the problems encountered in other systems. One such material, ${\mathrm{SrRuO}}_3$, is already widely used in various applications, but previous research has suggested that it loses its magnetism when less than a few atoms thick. Our experiments show, however, that a single layer of ${\mathrm{SrRuO}}_3$ remains magnetic and conductive if it is embedded in a block of ${\mathrm{Sr}\mathrm{T}\mathrm{i}\mathrm{O}}_3$.

We discover that replacing a single ${\mathrm{T}\mathrm{i}\mathrm{O}}_2$ plane of ${\mathrm{Sr}\mathrm{T}\mathrm{i}\mathrm{O}}_3$ by a ${\mathrm{RuO}}_2$ plane causes this layer to be a conducting, 2D magnet. Over a temperature range of 2–300 K, the resistivity of the ${\mathrm{SrRuO}}_3$ layer remains well below that seen in previous studies. We also observe magnetic hysteresis at temperatures below 25 K and hints of magnetism up to 100 K. This is the first realization of a conducting electron system in a complex oxide heterostructure that is confined to a single atomic layer.

Such atomically thin magnetic conductors could help improve the understanding of 2D magnetism. Because they are expected to be tunable by electric fields, such systems could also find use in active spintronics devices.