Stabilizing Ferromagnetism in Low-Dimensional Rare-Earth Manganites

The confinement of magnetism in atomically thin oxide layers has important implications for understanding and manipulating magnetic interactions in two-dimensional systems and for the realization of novel spintronic device architectures. In the rare-earth manganites which exhibit colossal magnetoresitive effects in bulk, a thickness-dependent suppression of magnetism has been observed for films with thicknesses on the order of 5-10 unit cells. By using synchrotron-based surface x-ray diffraction to image the atomic structures of ultra-thin manganite films, we identify polar structural relaxations at the manganite film interfaces which are correlated with the suppressed magnetism. We achieve robust ferromagnetism in unit cell-thick manganite films by using La_1-xSr_xCrO₃ spacers to effectively suppress the polar discontinuity at the manganite interfaces. These results demonstrate the control of atomic-scale structural distortions to engineer the electronic, orbital and magnetic properties of complex oxide systems.