The different types of magnetic coupling achieved via dimensionality control of interfacial charge transfer in cobaltite-cuprate superlattices

Abstract

The interface effect in artificial oxide heterostructures provides opportunities to engineer and explore desired functionalities associated with spintronic devices. Understanding the basic mechanism behind the interface effect is crucial for possible applications. Herein, charge-transfer-mediated magnetic coupling in LaCoO3/SrCuO2 (LCO/SCO) superlattices is investigated by changing the thickness of the SCO layer, which exhibits dimensional control of the structure transformation from planar-type to chain-type configuration. We found that the LCO/SCO superlattices display obvious soft-hard magnetic coupling when the SCO layer is thin, but the exchange bias effect gradually becomes dominant as thickness increases. As suggested by the x-ray absorption spectrum, electronic charge transfer dependent on SCO thickness is present at the interface of LCO/SCO superlattices. As the SCO is thin, the interaction of interfacial Co4+ and Co3+ results in the soft magnetic layer strongly coupling with the intrinsic hard magnetic layer of the LCO layer. But as the SCO layer thickens, charge transfer reduces, and the soft magnetic properties of the interface are suppressed. Instead, the long-range antiferromagnetic order of the bulk-like planar-type SCO layer couples with the adjacent ferromagnetic layer, leading to the exchange bias effect. Our results reveal an extraordinary spectrum of possibilities to design and engineer multifunctionalities of advanced oxide electronics.