Non-linear frequency and amplitude modulation of a nano-contact spin torque oscillator

TL;DR

This paper investigates how current-controlled modulation affects a nano-contact spin torque oscillator, revealing that standard theory accurately predicts frequency shifts, while combined non-linear modulation theory better explains sideband power.

Contribution

It provides a comprehensive analysis of non-linear frequency and amplitude modulation effects in spin torque oscillators, extending existing models to include combined non-linear effects.

Findings

Standard non-linear frequency modulation theory accurately predicts frequency shifts.

Sideband power matches predictions from combined non-linear frequency and amplitude modulation theory.

Different frequency non-linearity regimes significantly influence modulation behavior.

Abstract

We study the current controlled modulation of a nano-contact spin torque oscillator. Three principally different cases of frequency non-linearity ($d^{2}f/dI^{2}_{dc}$ being zero, positive, and negative) are investigated. Standard non-linear frequency modulation theory is able to accurately describe the frequency shifts during modulation. However, the power of the modulated sidebands only agrees with calculations based on a recent theory of combined non-linear frequency and amplitude modulation.