Defect-Mediated Bulk Dzyaloshinskii-Moriya Interaction in Ferromagnetic Multilayer Thin Films

The Dzyaloshinskii-Moriya interaction (DMI) in asymmetric multilayers is crucial for spintronics. However, it is also significant even in symmetric ones, and unveiling its atomic-level origin remains an issue. We use electron microscopy to propose defect-mediated bulk DMI in Pt/Co/Pt. We find an enhancement of the net DMI by increasing sputter gas pressure. The samples have a compositional gradient, but their compositional asymmetry is weak. Our analysis suggests that the asymmetric distribution of dislocations in the compositional gradient regions generates bulk DMI. Our results indicate the importance of bulk DMI in multilayers and could facilitate the development of spintronic devices.