Origin of interface magnetism in BiMnO3/SrTiO3 and LaAlO3/SrTiO3 heterostructures

TL;DR

This study reveals that interface magnetism in SrTiO3-based heterostructures with BiMnO3 and LaAlO3 arises from electron transfer and local magnetic moments, influenced by oxygen vacancies, providing insights into magnetic phenomena in complex oxides.

Contribution

It demonstrates the origin of interface magnetism in BiMnO3/SrTiO3 and LaAlO3/SrTiO3 heterostructures and highlights the role of oxygen vacancies and electron transfer in stabilizing magnetic order.

Findings

Magnetism is localized at the interface in both heterostructures.

Magnetic moments are associated with Ti3+ and Mn3+ ions.

Oxygen annealing quenches the magnetic moments in LaAlO3/SrTiO3.

Abstract

Possible ferromagnetism induced in otherwise non-magnetic materials has been motivating intense research in complex oxide heterostructures. Here we show that a confined magnetism is realized at the interface between SrTiO3 and two insulating polar oxides, BiMnO3 and LaAlO3. By using polarization dependent x-ray absorption spectroscopy, we find that in both cases the magnetic order is stabilized by a negative exchange interaction between the electrons transferred to the interface and local magnetic moments. These local magnetic moments are associated to Ti3+ ions at the interface itself for LaAlO3/SrTiO3 and to Mn3+ ions in the overlayer for BiMnO3/SrTiO3. In LaAlO3/SrTiO3 the induced magnetic moments are quenched by annealing in oxygen, suggesting a decisive role of oxygen vacancies in the stabilization of interfacial magnetism.