X-Ray Detection of Transient Magnetic Moments Induced by a Spin Current in Cu

TL;DR

This study uses x-ray spectro-microscopy to directly observe transient magnetic moments in copper caused by spin injection from cobalt, revealing insights into spin current effects at the atomic level.

Contribution

It provides the first direct detection and quantification of transient magnetic moments in Cu due to spin injection, distinguishing bulk and interface effects with elemental specificity.

Findings

Detected transient magnetic moments of 3×10^{-5} μ_B in Cu atoms due to spin accumulation.

Observed a 10% increase in interface magnetic moments caused by spin-torque effects.

Confirmed the dominance of spin-torque alignment over Joule heating effects during current flow.

Abstract

We have used a MHz lock-in x-ray spectro-microscopy technique to directly detect changes of magnetic moments in Cu due to spin injection from an adjacent Co layer. The elemental and chemical specificity of x-rays allows us to distinguish two spin current induced effects. We detect the creation of transient magnetic moments of $3\times 10^{-5}$ $\mu_\mathrm{B}$ on Cu atoms within the bulk of the 28 nm thick Cu film due to spin-accumulation. The moment value is compared to predictions by Mott's two current model. We also observe that the hybridization induced existing magnetic moments on Cu interface atoms are transiently increased by about 10% or $4\times 10^{-3}$ $\mu_\mathrm{B}$. This reveals the dominance of spin-torque alignment over Joule heat induced disorder of the interfacial Cu moments during current flow.