Long-range FMR driven spin pumping through a nonmagnetic insulator

TL;DR

This paper demonstrates long-range spin pumping from a ferrimagnetic insulator into a non-magnetic metal, challenging the traditional short-range exchange interaction model and suggesting magnetic dipole coupling as a possible mechanism.

Contribution

It reports the first observation of long-range spin pumping across an insulating barrier, revealing a new coupling mechanism beyond exchange interaction.

Findings

Spin pumping occurs over 200 nm distance, far beyond exchange interaction range.

Magnetic dipole coupling may mediate long-range spin transfer.

Potential for new spintronic devices utilizing long-range spin injection.

Abstract

Ferromagnetic resonance (FMR) driven spin pumping is an emerging technique for injection of a pure spin current from a ferromagnet (FM) into a non-magnetic (NM) material without an accompanying charge current. It is widely believed that this pumping proceeds exclusively via a short-range exchange interaction at the FM/NM interface. Here we report robust, long-range spin pumping from the ferrimagnetic double perovskite Sr2FeMoO6 (SFMO) into Pt across an insulating barrier up to 200 nm thick, and systematically rule out all known spurious effects. This result demonstrates dynamic spin injection over a distance far beyond the coupling range of the exchange interaction, exposing the need to consider other coupling mechanisms. The characteristic length scale for magnetic textures in Sr2FeMoO6 is approximately 150 nm, resulting from structural antiphase boundaries, thus raising the possibility that magnetic dipole coupling underlies the observed long range spin transfer. This discovery reveals a route to dynamic angular momentum transfer between a FM and a NM in the absence of mediation by itinerant electrons and promises new spin-functional devices employing long-range spin pumping.