# Atomic scale determination of magnetism and stoichiometry at the La0.7Sr0.3MnO3/SrTiO3 interface: investigation of inverse hysteresis

## TL;DR

This paper studies how magnetism and chemical composition change at the interface between two materials, revealing new insights into their electronic and magnetic properties.

## Contribution

The study provides atomic-scale evidence of interfacial magnetism and stoichiometry in La0.7Sr0.3MnO3/SrTiO3 heterostructures.

## Key findings

- A Mn3+-enriched interfacial layer forms in La0.7Sr0.3MnO3.
- Ti3+ induces ferromagnetism at the La0.7Sr0.3MnO3/SrTiO3 interface.
- Inverse hysteresis is due to remanent field, not antiferromagnetic coupling.

## Abstract

Controlling the correlations and electronic reconstruction at the interface of transition metal oxide heterostructures provides a new pathway for tuning their unique physical properties. Here, we investigate the effects of interfacial nonstoichiometry and vertical phase separation on the magnetic properties and proximity-induced magnetism of epitaxial La0.7Sr0.3MnO3 (LSMO)/SrTiO3(001) oxide heterostructures. We also reinvestigate the recently observed inverse hysteresis behavior reported for this system, which we find emanates from the remanent field of the superconducting solenoid and not from antiferromagnetic intra-layer exchange coupling in low coercivity LSMO thin films. Combined atomically resolved electron energy loss spectroscopy, element-specific X-ray magnetic circular dichroism, and interface-sensitive polarized soft X-ray resonant magnetic reflectivity show the formation of a Mn3+-enriched interfacial LSMO layer, of a Ti3+-derived magnetic interface layer coupled ferromagnetically to La0.7Sr0.3MnO3, together with a small density of O-vacancies at the interface. These results not only advance the understanding of the magnetism and spin structure of correlated oxide interfaces but also hold promise for practical applications, especially in devices where the performance relies on the control and influence of spin polarization currents by the interfacial spin structure.

Controlling stoichiometry and electronic reconstruction at the interface of transition metal oxide heterostructures offers a new way to tune their unique properties, leading to behaviors distinct from the bulk components. Using atomically resolved scanning transmission electron microscopy, element specific x-ray resonant magnetic reflectivity and x-ray magnetic circular dichroism, we have demonstrated that the presence of local oxygen deficiency across the interface and charge transfer to the empty conduction band of SrTiO3 at the interface are the primary drivers for the modified interfacial magnetism in the manganite thin films and Ti3+ induced ferromagnetism at the La0.7Sr0.3MnO3/SrTiO3 interface.