Single-spin spectroscopy of spontaneous and phase-locked spin torque oscillator dynamics

TL;DR

This paper uses N-V magnetometry to study the magnetic dynamics of a ferromagnetic nanowire driven by spin-orbit torques, revealing both macrospin and complex behaviors, and introduces a new microscopy modality.

Contribution

It demonstrates the use of N-V magnetometry to analyze spin torque oscillator dynamics and uncovers phenomena beyond simple models, including mode interactions and phase-locking.

Findings

Detection of spontaneous and phase-locked magnetic oscillations

Identification of additional spin wave modes and interactions

Development of a macrospin model capturing key features

Abstract

We employ N-$V$ magnetometry to measure the stray field dynamics of a ferromagnetic permalloy nanowire driven by spin-orbit torques. Specifically, we observe the optically detected magnetic resonance (ODMR) signatures of both spontaneous DC-driven magnetic oscillations and phase-locking to a second harmonic drive, developing a simple macrospin model that captures the salient features. We also observe signatures of dynamics beyond the macrospin model, including an additional ODMR feature (associated with a second SW mode) and one mode sapping power from another. Our results provide additional insight into N-$V$-spin wave coupling mechanisms, and represent a new modality for sub-wavelength N-$V$ scanned probe microscopy of nanoscale magnetic oscillators.