LaAlO$_3$/SrTiO$_3$: a tale of two magnetisms

TL;DR

This chapter reviews experimental evidence of two distinct types of magnetism at the LaAlO3/SrTiO3 interface, involving local magnetic moments and electron-electron interactions, and discusses their possible origins and effects.

Contribution

It categorizes magnetic phenomena at the interface into two types and discusses potential sources and mechanisms, providing a comprehensive framework for understanding these magnetic effects.

Findings

Magnetic phases involve local moments and their coupling to electrons.

Metamagnetic effects are mediated by electron-electron interactions without local moments.

Oxygen vacancies are a potential source of local magnetic moments.

Abstract

This book chapter reviews the experimental evidence for magnetic phenomena at the LaAlO3/SrTiO3 interface. We argue that essentially all of the signatures of magnetism can be sorted into two distinct categories: (1) magnetic phases (e.g., ferromagnetic or Kondo) involving local magnetic moments and their coupling to itinerant electrons; (2) metamagnetic effects that are mediated by attractive electron-electron interactions that do not involve local moments. We review possible candidates for the local moments that give rise to the ferromagnetic phases and focus on arguments for one potential source: oxygen vacancies. For the metamagnetic transport signatures, band-structure effects (e.g., Lifshitz transition) and strong attractive electron-electron interaction can help consolidate disparate experimental findings.