Real-space Observation of Ferroelectrically Induced Magnetic Spin Crystal in SrRuO₃

Unusual features in the Hall Resistivity of thin film systems are frequently associated with whirling spin textures such as Skyrmions. A host of recent investigations of Hall Hysteresis loops in SrRuO₃ heterostructures have provided conflicting evidence for different causes for such features. We have constructed an SrRuO₃-PbTiO₃ (Ferromagnetic–Ferroelectric) bilayer that exhibits features in the Hall Hysteresis previously attributed to a Topological Hall Effect (THE), and Skyrmions. We have employed field dependent Magnetic Force Microscopy measurements throughout the key fields where the ‘THE’ presents, revealing not Skyrmions, but the emergence of two periodic chiral spin textures. First, a zero-field cycloidal phase, which then transforms into a ‘double-q’ incommensurate spin crystal over the ‘THE-like’ field region, finally developing into a ferromagnetic switching regime as the sample reaches saturation, and the ‘THE-like’ diminishes. Scanning Tunnelling Electron Microscopy and DFT was used to observe and analyse surface inversion symmetry breaking and confirm the role of an interfacial Dzyaloshinskii–Moriya interaction at the heart of the system.