Strain tunable magnetism at ferroelastic domain walls

The ability to write, erase and move domain walls between ferroelastic domains paves the way for making nanoelectronics where the domain wall is the device. Little is, however, known about the magnetic properties of the ferroelastic domain walls. A fascinating model system is SrTiO3 where the ferroelastic domain walls display strain tunable polarity and enhanced conductivity besides being likely to host paired electrons existing both in the superconducting and nonsuperconducting state. Here, we reveal a long-range ferromagnetic order with stripy modulations along the ferroelastic domain walls in SrTiO3 and SrTiO3-based heterointerfaces using a scanning superconducting quantum interference device. The magnetism is coupled to high-mobility itinerant electrons with clear signatures in magnetotransport measurements. Strikingly, the magnetic state is also coupled dynamically to the lattice and can be reversibly tuned by applying local external forces. The study opens up for designing nanoscale devices based on domain walls where strain-tunable ferroelectric, ferroelastic and ferromagnetic orders may coexist.