Amplitude-Phase Coupling in a Spin-Torque Nano-Oscillator

TL;DR

This paper models a spin-torque nano-oscillator with thermal noise using Hopf bifurcation theory, calculating the amplitude-phase coupling factor from the Landau-Lifshitz-Gilbert-Slonczewski equation, revealing its dependence on in-plane anisotropy.

Contribution

It introduces a reduction method to compute the amplitude-phase coupling factor considering nonlinear damping, highlighting its variability with anisotropy.

Findings

Amplitude-phase coupling factor varies significantly with in-plane anisotropy.

The coupling factor influences the power spectrum of the oscillator.

The model incorporates thermal fluctuations and nonlinear damping effects.

Abstract

The spin-torque nano-oscillator in the presence of thermal fluctuation is described by the normal form of the Hopf bifurcation with an additive white noise. By the application of the reduction method, the amplitude-phase coupling factor, which has a significant effect on the power spectrum of the spin-torque nano-oscillator, is calculated from the Landau-Lifshitz-Gilbert-Slonczewski equation with the nonlinear Gilbert damping. The amplitude-phase coupling factor exhibits a large variation depending on in-plane anisotropy under the practical external fields.