Voltage control of frequency, effective damping and threshold current in nano-constriction-based spin Hall nano-oscillators

TL;DR

This study uses micromagnetic simulations to explore how voltage-controlled magnetic anisotropy and gate width influence the behavior of nano-constriction spin Hall nano-oscillators, revealing regimes of confinement, tuning, and separation.

Contribution

It demonstrates how VCMA and gate width can be used to control magnetodynamics and damping, enabling efficient voltage tuning over a large frequency range in SHNOs.

Findings

Effective damping can be increased tenfold with optimal gate width.

Voltage control remains effective across a broad frequency spectrum.

Different regimes of magnetodynamics are identified based on VCMA and gate width.

Abstract

Using micromagnetic simulations, we study the interplay between strongly voltage-controlled magnetic anisotropy (VCMA), $\Delta K = \pm$200 kJ/m$^3$, and gate width, $w=$ 10--400 nm, in voltage-gated W/CoFeB/MgO based nano-constriction spin Hall nano-oscillators. The VCMA modifies the local magnetic properties such that the magnetodynamics transitions between regimes of \emph{i}) confinement, \emph{ii}) tuning, and \emph{iii}) separation, with qualitatively different behavior. We find that the strongest tuning is achieved for gate widths of the same size as the the constriction width, for which the effective damping can be increased an order of magnitude compared to its intrinsic value. As a consequence, voltage control remains efficient over a very large frequency range, and subsequent manufacturing advances could allow SHNOs to be easily integrated into next-generation electronics for further fundamental studies and industrial applications.