Exceptionally Strong Spin-Transfer in Single Ni Nanoparticles

TL;DR

This study demonstrates exceptionally efficient spin-transfer in single Ni nanoparticles at cryogenic temperatures, driven by mesoscopic spin-orbit torques, with rates comparable to charge transfer and significantly higher than in larger magnets.

Contribution

It provides new insights into spin-transfer mechanisms at the nanoscale, highlighting the role of mesoscopic spin-orbit torques in enhancing efficiency.

Findings

Spin-transfer rates are comparable to charge-transfer rates in Ni nanoparticles.

Significant enhancement of spin-transfer efficiency over larger magnets.

Evidence of high spin-transfer rates in low magnetic fields due to spin-orbit effects.

Abstract

This letter presents studies of spin-transfer efficiency in electron transport via discrete electron-in- a-box levels in individual nanometer-scale Ni particles at 0.06K temperature. In a strong magnetic field, the spin-transfer rates are estimated by measuring the amplitudes of the Zeeman splitting of the levels. We find that the spin- and the charge-transfer rates are comparable, demonstrating significant enhancement of the spin-transfer efficiency compared to that in larger magnets. In a low magnetic field, we find an additional energy splitting as evidence that the spin-transfer rate is far higher than the charge-transfer rate. The effect is explained in terms of the strong mesoscopic spin- orbit torques, which are exerted on the magnetization in response to sequential electron tunneling.