Confined Magnetization at the Sublattice‐Matched Ruthenium Oxide Heterointerface

Creating a heterostructure by combining two magnetically and structurally distinct ruthenium oxides is a crucial approach for investigating their emergent magnetic states and interactions. Previously, research has predominantly concentrated on the intrinsic properties of the ferromagnet SrRuO₃ and recently discovered altermagnet RuO₂ solely. Here, the study engineers an ultrasharp sublattice-matched heterointerface using pseudo-cubic SrRuO₃ and rutile RuO₂, conducting an in-depth analysis of their spin interactions. Structurally, to accommodate the lattice symmetry mismatch, the inverted RuO₂ layer undergoes an in-plane rotation of 18 degrees during epitaxial growth on SrRuO₃ layer, resulting in an interesting and rotational interface with perfect crystallinity and negligible chemical intermixing. Performance-wise, the interfacial layer of 6 nm in RuO₂ adjacent to SrRuO₃ exhibits a nonzero magnetic moment, contributing to an enhanced anomalous Hall effect (AHE) at low temperatures. Furthermore, the observations indicate that in contrast to SrRuO₃ single layers, the AHE of [(RuO₂)₁₅/(SrRuO₃)_n] heterostructures show nonlinear behavior and reaches its maximum when the SrRuO₃ thickness reaches tens of nm. These results suggest that the interfacial magnetic interaction surpasses that of all-perovskite oxides (≈5-unit cells). This study underscores the significance and potential applications of magnetic interactions based on the crystallographic asymmetric interfaces in the design of spintronic devices.