Strain-induced frequency pulling in CoFeB/Cu/Py double-vortex oscillators

TL;DR

This paper demonstrates how piezostrain can induce frequency pulling in double-vortex spintronic oscillators, with the effect tunable by spacer thickness and strain, enabling enhanced control over their dynamical behavior.

Contribution

It reveals strain-induced frequency pulling in double-vortex structures and how spacer thickness influences this effect, offering new control mechanisms for spintronic oscillator synchronization.

Findings

Strain causes frequency downshift in magnetostrictive vortex.

Reduced spacer thickness enhances dipolar coupling and frequency pulling.

Strain can upshift the nonmagnetostrictive vortex frequency towards the magnetostrictive vortex.

Abstract

We demonstrate piezostrain-induced frequency pulling in stacked double-vortex structures, magnetostatically coupled through the nonmagnetic spacer. We study the effect of the Cu spacer thickness on the strain-induced gyrotropic frequency shift in double-vortex structures comprising of magnetostrictive CoFeB and nonmagnetostricitve Py layers. For the two stacked vortices with different eigen-frequencies, the strain-induced magnetoelastic anisotropy leads to the downshift of the gyration frequency of the magnetostricitve vortex. We show that for increased dipolar coupling between the layers (i.e. decreased spacer thickness), a strain-induced frequency pulling regime is obtained, where the resonance frequency of the nonmagnetostrictive Py vortex is upshifted towards the gyration resonance of the magnetostrictive CoFeB vortex. This result offers an additional degree of freedom for the manipulation of the dynamical regimes and synchronization conditions in spintronic oscillators, controlled by voltage and tunable by strain