Spin-Scattering Rates in Metallic Thin Films Measured by Ferromagnetic Resonance Damping Enhanced by Spin-Pumping

TL;DR

This study measures spin-transport properties in Pd and Pt thin films using ferromagnetic resonance damping enhanced by spin-pumping, revealing the relationship between charge and spin scattering and validating models of spin relaxation.

Contribution

It provides experimental determination of spin-diffusion lengths in Pd and Pt and compares different models for spin- and momentum-scattering rates in these materials.

Findings

Spin-diffusion lengths for Pt and Pd were obtained.

Dyakanov-Perel model best fits the data.

Spin-scattering time can be shorter than momentum scattering time in Pt.

Abstract

We determined the spin-transport properties of Pd and Pt thin films by measuring the increase in ferromagnetic resonance damping due to spin-pumping in ferromagnetic (FM)-nonferromagnetic metal (NM) multilayers with varying NM thicknesses. The increase in damping with NM thickness depends strongly on both the spin- and charge-transport properties of the NM, as modeled by diffusion equations that include both momentum- and spin-scattering parameters. We use the analytical solution to the spin-diffusion equations to obtain spin-diffusion lengths for Pt and Pd. By measuring the dependence of conductivity on NM thickness, we correlate the charge- and spin-transport parameters, and validate the applicability of various models for momentum-scattering and spin-scattering rates in these systems: constant, inverse-proportional (Dyakanov-Perel), and linear-proportional (Elliot-Yafet). We confirm previous reports that the spin-scattering time can be shorter than the momentum scattering time in Pt, and the Dyakanov-Perel-like model is the best fit to the data.