Electrically tunable long-distance transport in crystalline antiferromagnetic iron oxide

Abstract

Spintronics uses spins, the intrinsic angular momentum of electrons, as an alternative for the electron charge. Its long-term goal is to develop beyond-Moore, low-dissipation technology devices, recently demonstrating long-distance transport of spin signals across ferromagnetic insulators 1. Antiferromagnetically ordered materials, the most common class of magnetic materials, have several crucial advantages over ferromagnetic systems 2. Antiferromagnets exhibit no net magnetic moment, rendering them stable and impervious to external fields. Additionally, they can be operated at THz frequencies 3. Although their properties bode well for spin transport 4– 7, previous indirect observations indicate that spin transmission through antiferromagnets is limited to only a few nanometers 8– 10. Here we demonstrate the long-distance propagation of spin-currents through single-crystalline hematite (α-Fe ₂O ₃) 11, 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, tuning the antiferromagnetic resonance frequency with an external magnetic field 12. This simple antiferromagnetic insulator conveys spin information parallel to the Néel 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 1. Our results pave the way to ultra-fast, low-power antiferromagnet-insulator-based spin-logic devices 6, 13 that operate, without magnetic fields, at room temperature.