Investigating polar and magnetic coupling in PbTiO₃/SrRuO₃ heterostructures

Coupling between polar and magnetic orders in multiferroics represents a fundamental challenge in condensed matter physics. Such coupling typically arises at the atomic scale through local interactions between polar lattice distortions and variations in magnetic exchange pathways. In this work, we investigate the coupling between nanoscale polar super textures and ferromagnetic order in (PbTiO₃)₁₆/(SrRuO₃)₉ heterostructures grown on DyScO₃ (110) substrates. Under the appropriate strain conditions, the PbTiO₃ layers form polar vortices with an ∼11 nm periodicity, and we confirm that the resulting nanoscale in-plane strain modulation extends into the SrRuO₃ layer. Furthermore, we probe direct charge excitations within the Sr and Ru sublattices, which are strongly coupled at the interface, using resonant soft X-ray diffraction. This reveals that the Sr lattice coupling extends deeper into PTO compared to the Ru sublattice. The atomistic modeling shows a great agreement with our experimental results. These results provide new insight into engineering nanoscale modulations of magnetic order through interfacial coupling in complex oxide heterostructures.

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