  Interfaces between correlated complex oxides are promising avenues to realize
new forms of magnetism that arise as a result of charge transfer, proximity
effects and locally broken symmetries. We report upon the discovery of a
non-collinear magnetic structure in superlattices of the ferromagnetic metallic
oxide La2/3Sr1/3MnO3 (LSMO) and the correlated metal LaNiO3 (LNO). The exchange
interaction between LSMO layers is mediated by the intervening LNO, such that
the angle between the magnetization of neighboring LSMO layers varies in an
oscillatory manner with the thickness of the LNO layer. The magnetic field,
temperature, and spacer thickness dependence of the non-collinear structure are
inconsistent with the bilinear and biquadratic interactions that are used to
model the magnetic structure in conventional metallic multilayers. A model that
couples the LSMO layers to a helical spin state within the LNO fits the
observed behavior. We propose that the spin-helix results from the interaction
between a spatially varying spin susceptibility within the LNO and interfacial
charge transfer that creates localized Ni2+ states. This provides a new
approach to engineering non-collinear spin textures in metallic oxide
heterostructures that can be exploited in devices based on both spin and charge
transport.
