Strong linewidth variation for spin-torque nano-oscillators as a function of in-plane magnetic field angle

TL;DR

This study investigates how the linewidth of microwave signals from spin-torque nano-oscillators varies significantly with the in-plane magnetic field angle, revealing a transition from incoherent to coherent precession.

Contribution

It demonstrates the strong dependence of linewidth on magnetic field angle and links this to a transition in precession coherence through micromagnetic simulations.

Findings

Linewidth decreases by over 20 times when rotating the magnetic field.

Transition from spatially incoherent to coherent precession identified.

Micromagnetic simulations support experimental observations.

Abstract

We measure the microwave signals produced by spin-torque-driven magnetization dynamics in patterned magnetic multilayer devices at room temperature, as a function of the angle of a magnetic field applied in the sample plane. We find strong variations in the frequency linewidth of the signals, with a decrease by more than a factor of 20 as the field is rotated from the magnetic easy axis to the in-plane hard axis. Based on micromagnetic simulations, we identify these variations as due to a transition from spatially incoherent to coherent precession.