Controlling entangled spin-orbit coupling of 5d states with interfacial heterostructure engineering

The combination of strong electron correlations in $3d$ transition-metal oxides and spin-orbit interactions in the $5d$ counterpart can give rise to exotic electronic and magnetic properties. Here, the nature of emerging phenomena at the interface between $\mathrm{SrIr}{\mathrm{O}}₃$ (SIO) and $\mathrm{L}{\mathrm{a}}_2/3\mathrm{S}{\mathrm{r}}_1/3\mathrm{Mn}{\mathrm{O}}₃$ (LSMO) is presented. Nominally, SIO with strong spin-orbit interaction is metallic and nonmagnetic on the verge of a metal-insulator transition, whereas LSMO is metallic and ferromagnetic with itinerant character and high spin polarization. In the 1:1 LSMO/SIO superlattice, we observe ferromagnetic Mn moments with an insulating behavior, accompanied by antiferromagnetic ordering in SIO. Element-resolved x-ray magnetic circular dichroism proves that there is a weak net ferromagnetic Ir moment aligned antiparallel to the Mn counterpart. The branching ratio shows the formation of molecular orbitals between the Mn and Ir layers modifying the Ir $5d$ electronic configuration through the mixture of ${t}_2g$ and ${e}_g$ states, resulting in a deviation from ${J}_{\mathrm{eff}}=1/2$. This result demonstrates a pathway to manipulate the spin-orbit entanglement in $5d$ states with two-dimensional $3d$ spin-polarized electrons through heterostructure design.