Giant orbital magnetoresistance in the antiferromagnet CoO driven by dynamic orbital angular momentum interaction

TL;DR

This study demonstrates a significant enhancement in orbital Hall magnetoresistance in CoO/Cu* due to dynamic orbital angular momentum interactions, revealing new possibilities for orbitronics and energy-efficient antiferromagnetic devices.

Contribution

It introduces a novel interaction mechanism between dynamic orbital angular momentum and static orbital moments in CoO, enabling harnessing giant orbital currents in orbitronics.

Findings

Over fifty-fold increase in orbital Hall magnetoresistance in CoO/Cu*

Sign reversal of orbital magnetoresistance at the CoO interface

Potential for energy-efficient orbitronics using orbital angular momentum-dominated materials

Abstract

Recent predictions of orders of magnitude larger orbital current effects compared to spin currents have attracted significant interest. However, the full potential of giant orbital currents remains to be fully harnessed, since so far, the orbital currents need to be converted into spin currents before they can interact with the static magnetization that is dominated by spin angular momentum in conventional magnets. By using a magnet dominated by orbital angular momentum, we demonstrate a more than fifty-fold enhancement in orbital Hall magnetoresistance in CoO/Cu*, compared to conventional CoO/Pt. This is found to be driven by a unique interaction between dynamic orbital angular momentum from surface oxidized Cu* (i.e., the orbital current) and the static orbital angular momentum which constitutes the magnetic moments in the antiferromagnetic insulator CoO. A distinctive scattering mechanism for orbital currents at the CoO interface leads to a sign reversal in orbital magnetoresistance in CoO/Cu* compared to CoO/Pt. Our results show how by using orbital angular momentum-dominated materials such as CoO, we can harness the benefits of giant orbital currents that have not been possible using conventional spin-dominated magnets, for orbitronics-based devices, offering unprecedented energy efficiency for operations of antiferromagnets that combine ultimate stability with THz dynamics.