# Interfacial contributions to spin-orbit torque and magnetoresistance in ferromagnet/heavy-metal bilayers

## TL;DR

This paper investigates how interfacial effects influence spin-orbit torque and magnetoresistance in ferromagnet/heavy-metal bilayers, revealing significant interfacial contributions beyond the spin-Hall effect through first-principles calculations.

## Contribution

It introduces a detailed first-principles analysis of interfacial contributions to spin-orbit phenomena, highlighting their importance beyond traditional spin-Hall models.

## Key findings

- Damping-like torque has both spin-Hall and interfacial contributions.
- Magnetoconductance exceeds spin-Hall model predictions by over an order of magnitude.
- Interfacial effects play a major role in spin-orbit torque and magnetoresistance.

## Abstract

The thickness dependence of spin-orbit torque and magnetoresistance in ferromagnet/heavy-metal bilayers is studied using the first-principles non-equilibrium Green's function formalism combined with the Anderson disorder model. A systematic expansion in orthogonal vector spherical harmonics is used for the angular dependence of the torque. The damping-like torque in Co/Pt and Co/Au bilayers can be described as a sum of the spin-Hall contribution, which increases with thickness in agreement with the spin-diffusion model, and a comparable interfacial contribution. The magnetoconductance in the plane perpendicular to the current in Co/Pt bilayers is of the order of a conductance quantum per interfacial atom, exceeding the prediction of the spin-Hall model by more than an order of magnitude. This suggests that the "spin-Hall magnetoresistance," similarly to the damping-like torque, has a large interfacial contribution unrelated to the spin-Hall effect.