Direct linking of interfacial and interlayer chiral exchange coupling observed through interface tuning

In recent years, spintronics research has expanded from collinear to noncollinear magnetism, driving increased interest in the interlayer Dzyaloshinskii–Moriya interaction (IL-DMI) for its role in mediating long-range chiral coupling between magnetic layers. While IL-DMI enables vertical transmission of chirality in multilayers, its microscopic origin remains less understood, particularly in relation to the well-studied interfacial DMI. Establishing whether these two forms of Dzyaloshinskii–Moriya interaction share a common underlying mechanism is essential for the unified control of chiral spin textures in engineered heterostructures. Here, we demonstrate unambiguous polarity reversal of IL-DMI by tuning the ferromagnetic composition of the perpendicularly magnetized layer in a type-T structure composed of Co and Ni interfaced with Pt. The polarity shift correlates with transitioning from a Co to a Ni-dominated interface. Control experiments confirm that the IL-DMI direction is exclusively determined by the identity of the ferromagnetic layer in direct contact with the Pt spacer and remains unaffected by the overall ferromagnetic material thickness. Robust field-free switching, with polarity directly following this interface-defined IL-DMI direction, further reinforces the interfacial origin of the chiral coupling. These findings establish interfacial composition as a key handle for engineering chiral coupling in spintronic multilayers.