Electronic reconstruction and spontaneous magnetic reversal driven by interface dipole layer*

Between two insulators, the electric dipole formed at the polar-nonpolar interface, triggers charge transfer that results in emergent phenomena. However, at metal-insulator junctions, a polar-nonpolar interface behaves very differently. We show that in this case, itinerant electronic screening becomes indispensable. The caveat to this premise is that, within the Thomas-Fermi screening length, the charge transfer is non-negligible. To illustrate this effect, we performed a detailed study of La_0.67Sr_0.33MnO₃/SrTiO₃ (001). Electronic reconstruction and subtle lattice distortion at the interface creates a strong antiferromagnetic (AFM) exchange coupling, producing an exchange-spring type interaction. Surprisingly, the AFM coupled layers at the interface prompt a spontaneous magnetic reversal and an inverted hysteresis persisting above room temperature. Our results demonstrate that an interface dipole leads to magnetic switching in a monolithic thin film, showing a new design pathway that activates the interface, on the length scale of Thomas-Fermi screening, a single unit cell.