Interface exchange processes in LaAlO$_3$/SrTiO$_3$ induced by oxygen vacancies

TL;DR

This study investigates how oxygen vacancies influence the electronic and magnetic properties of LaAlO₃/SrTiO₃ interfaces using first-principles and model Hamiltonian methods, revealing defect-induced magnetic phases and orbital polarization effects.

Contribution

It provides a detailed theoretical analysis of oxygen vacancy effects on orbital and spin exchange, highlighting the interplay of Hubbard U and Hund's J in defect-induced correlated states.

Findings

Oxygen vacancies induce orbital polarization towards an $e_g$ state.

Different magnetic phases emerge depending on vacancy concentration.

Defect manipulation can tailor magnetic properties at oxide interfaces.

Abstract

Understanding the role of defects in oxide heterostructures is crucial for future materials control and functionalization. We hence study the impact of oxygen vacancies (OVs) at variable concentrations on orbital- and spin exchange in the LaAlO$_3$/SrTiO$_3$ interface by first principles many-body theory and real-space model-Hamiltonian techniques. Intricate interplay between Hubbard $U$ and Hund's coupling $J_{\rm H}$ for OV-induced correlated states is demonstrated. Orbital polarization towards an effective $e_g$ state with predominant local antiferromagnetic alignment on Ti sites near OVs is contrasted with $t_{2g}(xy)$ states with ferromagnetic tendencies in the defect-free regions. Different magnetic phases are identified, giving rise to distinct net-moment behavior at low and high OV concentrations. This provides a theoretical basis for prospective tailored magnetism by defect manipulation in oxide interfaces.