Emergent Magnetic Phenomena in Iridate-Based Superlattices*

Heterointerfaces of complex oxides provide a rich playground to explore emergent phenomena that are not found in the bulk and have been largely studied in 3d transition metal oxide (TMO) heterostructures. With recent advances in the synthesis of 5d TMOs, heterostructures based on 3d and 5d TMOs offer new model systems to realize emergent functionalities of complex oxides. In this talk, we demonstrate emergent magnetism and perpendicular magnetic anisotropy in iridate-based superlattices. We focus on superlattices comprised of the colossal magnetoresistive La_1-xSr_xMnO₃ (LSMO) and the paramagnetic SrIrO₃. Weak ferromagnetism and a new spin-orbit state are induced in SrIrO₃ due to dimensional confinement and interfacial coupling. On the other hand, LSMO shows ferromagnetism in superlattices for all compositions of x (x=0, 0.3, 0.5, 0.8, 1.0). The stabilization of ferromagnetism in both La rich and Sr rich superlattices points to an interfacial charge transfer which is confirmed by x-ray absorption spectroscopy measurements. Surprisingly, we find a strong interface-induced perpendicular magnetic anisotropy (PMA) for Sr rich compositions. The PMA changes as a function of x. Synchrotron x-ray diffraction and linear dichroism measurements indicate a strong correlation between the PMA and the oxygen octahedral rotations at interfaces. Our comprehensive study provides insights into unique emergent phenomena driven by the 3d-5d heterointerfaces due to the delicate interplay of charge, spin, orbital and lattice degrees of freedom. The emergence of a strong PMA also points to the potential of its incorporation in future spintronic applications.