Parametric instability of a magnetic junction under modulated spin-polarized current

TL;DR

This paper analyzes the stability of magnetic junction configurations under amplitude-modulated spin-polarized current, revealing conditions for parametric resonance-induced instability and its suppression by direct current.

Contribution

It provides a theoretical analysis of parametric instability in magnetic junctions under modulated currents, highlighting resonance conditions and experimental relevance.

Findings

Parametric resonance occurs when modulation frequency is twice the precession frequency.

Parametric instability lowers the threshold of dc current density for instability.

High-frequency current can suppress parametric instability through nonparametric effects.

Abstract

The stability is analyzed of the magnetic junction collinear configurations against small fluctuations under amplitude-modulated current with CPP mode. High spin injection is assumed. Under parametric resonance conditions, with the modulation frequency twice the precession frequency, instability is possible of one, or another, or both the collinear configurations. When the dc component of the current density exceeds the instability threshold of the antiparallel configuration, the parametric instability is suppressed by nonparametric one which is induced by the dc current. The parametric instability manifests itself as lowering the threshold of the dc current density in presence of the high-frequency current, such an effect has been observed in experiments repeatedly.