# Low offset frequency $1/f$ flicker noise in spin torque vortex oscillators

## TL;DR

This paper investigates the low offset frequency flicker noise in spin torque vortex oscillators, combining theoretical expansion of nonlinear auto-oscillator theory with experimental measurements to understand its impact on frequency stability.

## Contribution

It introduces a phenomenological expansion of nonlinear auto-oscillator theory and provides experimental analysis of $1/f$ flicker noise in TMR-based spin-torque vortex oscillators.

## Key findings

- Theoretical predictions align with experimental flicker noise measurements.
- Nonlinear dynamics influence the flicker noise characteristics.
- Magnetoresistance variations contribute to the observed noise.

## Abstract

Low frequency noise close to the carrier remains little explored in spin torque nano oscillators. However, it is crucial to investigate as it limits the oscillator's frequency stability. This work addresses the low offset frequency flicker noise of a TMR-based spin-torque vortex oscillator in the regime of large amplitude steady oscillations. We first phenomenologically expand the nonlinear auto-oscillator theory aiming to reveal the properties of this noise. We then present a thorough experimental study of the oscillator's $1/f$ flicker noise and discuss the results based on the theoretical predictions. Hereby, we connect the oscillator's nonlinear dynamics with the concept of flicker noise and furthermore refer to the influence of a standard $1/f$ noise description based on the Hooge formula, taking into account the non-constant magnetic oscillation volume, which contributes to the magnetoresistance.