Spin-torque oscillator linewidth narrowing under current modulation

TL;DR

This paper demonstrates that applying radio frequency current modulation to a spin torque oscillator significantly narrows its linewidth by leveraging nonlinear frequency shift effects, enhancing oscillator stability.

Contribution

It introduces a method to reduce STO linewidth through current modulation exploiting nonlinear frequency shift, with quantitative analysis linking free-running behavior to linewidth narrowing.

Findings

Linewidth reduced by up to 85% under modulation

Nonlinear frequency shift is key to linewidth reduction

Quantitative model matches experimental results

Abstract

We study the behavior of the linewidth of a nano-contact based spin torque oscillator (STO) under application of a radio frequency (100 MHz) modulating current. We achieve a significant (up to 85%) reduction of the STO linewidth when it is modulated across a region of high nonlinearity. The mechanism responsible for the linewidth reduction is the nonlinear frequency shift under the influence of current modulation, which reduces the nonlinear amplification of the linewidth. The reduction of the linewidth during modulation can be quantitatively calculated from the free-running behavior of the STO.