Generalized analysis of thermally activated domain-wall motion in Co/Pt multilayers

TL;DR

This study experimentally investigates thermally activated domain-wall motion in Co/Pt multilayers, deriving a generalized Arrhenius equation, and assesses the impact of electric current and spin torque, revealing that ultrathin layers respond differently to current.

Contribution

It introduces a generalized Arrhenius-like model for thermally activated DW motion in multilayers and analyzes current-induced effects, highlighting differences based on Co layer thickness.

Findings

Activation energy depends on Curie temperature.

Current induces spin torque only in ultrathin Co layers.

Conventional spin-transfer torque does not drive DWs in thicker multilayers.

Abstract

Thermally activated domain-wall (DW) motion driven by magnetic field and electric current is investigated experimentally in out-of-plane magnetized Pt(Co/Pt)$_3$ multilayers. We directly extract the thermal activation energy barrier for DW motion and observe the dynamic regimes of creep, depinning, and viscous flow. Further analysis reveals that the activation energy must be corrected with a factor dependent on the Curie temperature, and we derive a generalized Arrhenius-like equation governing thermally activated motion. By using this generalized equation, we quantify the efficiency of current-induced spin torque in assisting DW motion. Current produces no effect aside from Joule heating in the multilayer with 7-\AA\ thick Co layers, whereas it generates a finite spin torque on DWs in the multilayer with atomically thin 3-\AA\ Co layers. These findings suggest that conventional spin-transfer torques from in-plane spin-polarized current do not drive DWs in ultrathin Co/Pt multilayers.