Spin wave mode coexistence on the nano-scale: A consequence of the Oersted field induced asymmetric energy landscape

TL;DR

This study demonstrates that the coexistence of multiple spin wave modes on the nanoscale is enabled by Oersted field-induced asymmetries and localization effects, challenging the notion that only one mode can dominate in such systems.

Contribution

It reveals the conditions under which multiple spin wave modes can coexist in nanocontact spin torque oscillators, highlighting the role of Oersted field asymmetries and localization.

Findings

Mode coexistence is facilitated by local field asymmetries.

Spatial separation of modes due to Oersted field effects.

Detection of a low frequency intermodulation signal.

Abstract

It has been argued that if multiple spin wave modes are competing for the same centrally located energy source, as in a nanocontact spin torque oscillator, that only one mode should survive in the steady state. Here, the experimental conditions necessary for mode coexistence are explored. Mode coexistence is facilitated by the local field asymmetries induced by the spatially inhomogeneous Oersted field, which leads to a physical separation of the modes, and is further promoted by spin wave localization at reduced applied field angles. Finally, both simulation and experiment reveal a low frequency signal consistent with the intermodulation of two coexistent modes.