Power and linewidth of propagating and localized modes in nanocontact spin-torque oscillators

TL;DR

This study investigates the power and linewidth of propagating and localized spin wave modes in nanocontact spin-torque oscillators, revealing their dependence on magnetic field angle and mode interactions.

Contribution

It provides experimental data and theoretical modeling of mode power and linewidth variations with magnetic field angle, highlighting mode coexistence and switching effects.

Findings

Propagating mode power increases monotonically with angle.

Localized mode power peaks near 40 degrees and vanishes near 58 degrees.

Linewidth broadening occurs due to mode switching in certain angles.

Abstract

Integrated power and linewidth of a propagating and a self-localized spin wave modes excited by spin-polarized current in an obliquely magnetized magnetic nanocontact are studied experimentally as functions of the angle $\theta_e$ between the external bias magnetic field and the nanocontact plane. It is found that the power of the propagating mode monotonically increases with $\theta_e$, while the power of the self-localized mode has a broad maximum near $\theta_e = 40$ deg, and exponentially vanishes near the critical angle $\theta_e = 58$ deg, at which the localized mode disappears. The linewidth of the propagating mode in the interval of angles $58<\theta_e<90$ deg, where only this mode is excited, is adequtely described by the existing theory, while in the angular interval where both modes can exist the observed linewidth of both modes is substantially broadened due to the telegraph switching between the modes. Numetical simulations and an approximate analytical model give good semi-quantitative description of the observed results.