Invariant form of spin-transfer switching condition

TL;DR

This paper derives an invariant condition for spin-transfer switching, revealing how current stability depends on spin torque divergence and providing new insights into experimental predictions and the limitations of common approximations.

Contribution

It introduces an invariant form of the switching condition in spin-transfer devices, linking stability to spin torque divergence and clarifying the role of energy saddle points.

Findings

Switching ability depends on spin torque divergence at energy minima and maxima.

Energy saddle points are stabilized by current-induced merging with other equilibria.

The approach predicts experimental outcomes and highlights limitations of existing approximations.

Abstract

We derive an invariant form of the current-induced switching condition in spin-transfer devices and show that for energy minima and maxima the "switching ability" of the current is determined by the spin torque divergence. In contrast, energy saddle points are normally stabilized by current-induced merging with other equilibria. Our approach provides new predictions for several experimental setups and shows the limitations of some frequently used approximations.