Confined Magnetization at the Sublattice‐Matched Ruthenium Oxide Heterointerface

Abstract 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 SrRuO 3 and recently discovered altermagnet RuO 2 solely. Here, the study engineers an ultrasharp sublattice‐matched heterointerface using pseudo‐cubic SrRuO 3 and rutile RuO 2 , conducting an in‐depth analysis of their spin interactions. Structurally, to accommodate the lattice symmetry mismatch, the inverted RuO 2 layer undergoes an in‐plane rotation of 18 degrees during epitaxial growth on SrRuO 3 layer, resulting in an interesting and rotational interface with perfect crystallinity and negligible chemical intermixing. Performance‐wise, the interfacial layer of 6 nm in RuO 2 adjacent to SrRuO 3 exhibits a nonzero magnetic moment, contributing to an enhanced anomalous Hall effect (AHE) at low temperatures. Furthermore, the observations indicate that in contrast to SrRuO 3 single layers, the AHE of [(RuO 2 ) 15 /(SrRuO 3 ) n ] heterostructures show nonlinear behavior and reaches its maximum when the SrRuO 3 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.