Theory of the spin-torque-driven ferromagnetic resonance in a ferromagnet/normal-metal/ferromagnet structure

TL;DR

This paper provides a theoretical analysis of current-driven ferromagnetic resonance in a ferromagnet/normal-metal/ferromagnet structure, explaining experimental observations and identifying two mechanisms for dc voltage generation.

Contribution

It introduces a theoretical framework that accounts for two mechanisms of dc voltage generation in current-driven ferromagnetic resonance, aligning with recent experimental results.

Findings

Both rectification of alternating current and spin current emission contribute equally to dc voltage.

The analysis explains experimental observations of ferromagnetic resonance in tri-layer structures.

The second mechanism's contribution is significant for thin ferromagnetic films.

Abstract

We present a theoretical analysis of current driven ferromagnetic resonance in a ferromagnet/normal-metal/ferromagnet tri-layer. This method of driving ferromagnetic resonance was recently realized experimentally by Tulapurkar et al. [Nature 438, 339 (2005)] and Sankey et al. [Phys. Rev. Lett. 96, 227601 (2006)]. The precessing magnetization rectifies the alternating current applied to drive the ferromagnetic resonance and leads to the generation of a dc voltage. Our analysis shows that a second mechanism to generate a dc voltage, rectification of spin currents emitted by the precessing magnetization, has a contribution to the dc voltage that is of approximately equal size for the thin ferromagnetic films used in the experiment.