The number of atomic layers confined in a two-dimensional structure is crucial for the electronic and magnetic properties. Single-layer and bilayer $J_{\mathrm{eff}}=1/2$ square lattices are well-known examples where the presence of the extra layer turns the $XY$ anisotropy to the $c$-axis anisotropy. We report on experimental realization of a hybrid ${\mathrm{SrIrO}}_3/{\mathrm{SrTiO}}_3$ superlattice that integrates monolayer and bilayer square lattices in one layered structure. By synchrotron x-ray diffraction, resonant x-ray magnetic scattering, magnetization, and resistivity measurements, we found that the hybrid superlattice exhibits properties that are distinct from both the single-layer and bilayer systems and cannot be explained by a simple addition of them. In particular, the entire hybrid superlattice orders simultaneously through a single antiferromagnetic transition at temperatures similar to the bilayer system but with all the $J_{\mathrm{eff}}=1/2$ moments mainly pointing in the $ab$ plane similar to the single-layer system. The results show that bringing monolayer and bilayer with orthogonal properties in proximity to each other in a hybrid superlattice structure is a powerful way to stabilize a unique state not obtainable in a uniform structure.

• Received 18 March 2022
• Revised 8 August 2022
• Accepted 26 September 2022

DOI:https://doi.org/10.1103/PhysRevLett.129.187201