Auto-oscillation threshold and line narrowing in MgO-based spin-torque oscillators

TL;DR

This paper experimentally investigates MgO-based spin-torque oscillators, revealing narrow spectral lines and an auto-oscillation threshold, with simulations identifying the excited mode as an edge mode of the synthetic antiferromagnet.

Contribution

It provides the first detailed experimental analysis of auto-oscillation thresholds and line narrowing in MgO-based spin-torque oscillators, supported by micromagnetic simulations.

Findings

Spectral lines as narrow as 8 MHz at 10.7 GHz

Clear evidence of an auto-oscillation threshold

Edge mode identified as the excited mode

Abstract

We present an experimental study of the power spectrum of current-driven magnetization oscillations in MgO tunnel junctions under low bias. We find the existence of narrow spectral lines, down to 8 MHz in width at a frequency of 10.7 GHz, for small applied fields with clear evidence of an auto-oscillation threshold. Micromagnetics simulations indicate that the excited mode corresponds to an edge mode of the synthetic antiferromagnet.