Orbital selective switching of ferromagnetism in an oxide quasi two-dimensional electron gas

TL;DR

This study reveals how orbital filling in oxide quasi-two-dimensional electron gases induces a switch from antiferromagnetic to ferromagnetic interactions, advancing understanding of magnetic phenomena in complex oxide interfaces.

Contribution

It demonstrates the orbital selective switching mechanism of ferromagnetism in oxide q2DEGs through combined theoretical and experimental methods.

Findings

Orbital filling of Ti 3d_xz,yz bands induces magnetic switching.

Carrier density influences ferromagnetic correlations.

The study explains anomalous Hall effects in the system.

Abstract

Multi-orbital physics in quasi-two-dimensional electron gases (q2DEGs) triggers unique phenomena not observed in bulk materials, such as unconventional superconductivity and magnetism. Here, we investigate the mechanism of orbital selective switching of the spin-polarization in the oxide q2DEG formed at the (001) interface between the LaAlO$_{3}$, EuTiO$_{3}$ and SrTiO$_{3}$ band insulators. By using density functional theory calculations, transport, magnetic and x-ray spectroscopy measurements, we find that the filling of titanium-bands with 3d$_{xz,yz}$ orbital character in the EuTiO3 layer and at the interface with SrTiO$_{3}$ induces an antiferromagnetic to ferromagnetic switching of the exchange interaction between Eu-4f$^{7}$ magnetic moments. The results explain the observation of the carrier density dependent ferromagnetic correlations and anomalous Hall effect in this q2DEG, and demonstrate how combined theoretical and experimental approaches can lead to a deeper understanding of novel electronic phases and serve as a guide for the materials design for advanced electronic applications.