Electrically controlled long-distance spin transport through an antiferromagnetic insulator

TL;DR

This paper demonstrates the long-distance transport of spin currents through an antiferromagnetic insulator, hematite, over tens of micrometers, using the spin Hall effect and external magnetic field tuning, advancing spintronics technology.

Contribution

It provides the first experimental evidence of long-range spin transport in an antiferromagnetic insulator, highlighting its potential for low-power spintronic devices.

Findings

Spin currents propagate over tens of micrometers in hematite.

Spin transport is controlled by interfacial spin-bias and magnetic field tuning.

Antiferromagnetic insulators can convey spin information as efficiently as ferromagnets.

Abstract

Spintronics uses spins, the intrinsic angular momentum of electrons, as an alternative for the electron charge. Its long-term goal is in the development of beyond-Moore low dissipation technology devices. Recent progress demonstrated the long-distance transport of spin signals across ferromagnetic insulators. Antiferromagnetically ordered materials are however the most common class of magnetic materials with several crucial advantages over ferromagnetic systems. In contrast to the latter, antiferromagnets exhibit no net magnetic moment, which renders them stable and impervious to external fields. In addition, they can be operated at THz frequencies. While fundamentally their properties bode well for spin transport, previous indirect observations indicate that spin transmission through antiferromagnets is limited to short distances of a few nanometers. Here we demonstrate the long-distance, over tens of micrometers, propagation of spin currents through hematite (\alpha-Fe2O3), the most common antiferromagnetic iron oxide, exploiting the spin Hall effect for spin injection. We control the spin current flow by the interfacial spin-bias and by tuning the antiferromagnetic resonance frequency with an external magnetic field. This simple antiferromagnetic insulator is shown to convey spin information parallel to the compensated moment (N\'eel order) over distances exceeding tens of micrometers. This newly-discovered mechanism transports spin as efficiently as the net magnetic moments in the best-suited complex ferromagnets. Our results pave the way to ultra-fast, low-power antiferromagnet-insulator-based spin-logic devices that operate at room temperature and in the absence of magnetic fields.